The Anthrobotics Cluster at the University of Edinburgh / The CRAG – Creation of Reality Group

Aram Vartanian

(in P. Weiner ed., Dictionary of the History of Ideas, vol. 3. New York: Scribner, 1973)


The man-machine idea occupies a strategic and fateful position at the confluence of several disciplines and traditions: in neurophysiology and psychology it is a fecund empirical hypothesis; in philosophy, it is a speculative option to resolve the body-mind problem; in technology, it expresses the demiurgic goal of mastering our environment; in sociology and the humanities, it often conveys the malaise of dehumanization in modern culture. This is a History of the idea that humans are also machines.

The term “man-machine” denotes the idea that the total psychic life of the individual can be properly described and explained as the product of his physical organization viewed as a mechanical system in structure and function. An account of the ramified history of the idea, however, requires a somewhat less rigid definition, which will in several instances pertain to the mechanization of only some, but not all, aspects of mental activity; whereas on other occasions it must be made broad enough to encompass the animal as well as man. Similarly, the notion of “machine,” in particular when used as an equivalent of the living organism, cannot be assigned in advance any precise or concrete sense that would hold good over the entire length of this study. The history of the man-machine is in large part that of the relativity of the concept of mechanism, as it has been understood with increasing breadth and refinement, from Greek times to our own day, in those sciences that have had a decisive influence on the shaping and scope of the idea in question, namely, physics, biology, medicine, technology, and (more recently) chemistry and psychophysiology. Moreover, in its relations to philosophy the fortunes of the man-machine may be regarded as having closely conformed, up to and since its first thoroughly consistent exposition by La Mettrie in 1747, to the general curve followed by the growth of materialism. However, it would be historically sounder to eschew an absolute linkage between the man-machine idea and any ultimate materialistic position of a metaphysical kind, despite the strong affinities that persist logically between the two notions.

The man-machine is typically a modern doctrine, but it is necessary to go back to ancient Greece in order to discover both the speculative tendency and the positive elements from which it evolved. Quite early in Greek thought the attempt was made to conceive of the soul as an organized function of matter. Some Pythagoreans spoke of it, for example, as the “harmony of the body,” even if such a notion had for them perhaps a more mystical than scientific meaning. In Empedocles (ca. 490-30 B.C.), however, we already find the rudiments of a psychology of sensation based on exclusively physical factors. The external world, viewed as continuous in substance with the organs of sense, was described by him as registering replicas of things (simulacra) directly on the senses in the form of perceptions. This precocious empiricism, probably indebted to the medical writings of Alcmeon, remained tied to the error, prevalent in antiquity, that the heart rather than the brain served as the sensorium commune. There was, nevertheless, a glimmer of the man-machine in the Empedoclean opinion that the varieties of psychic constitution among men, including their different aptitudes and characters, depend, as decreed by the cardio-sensory theory, on the composition of their blood, that is, on the size, distribution, and combination of the particles assumed to compose it.

Epicureanism carried out to its conclusion, within the technical limits imposed by Greek science, the type of psychophysical explanation initiated by Empedocles, and in so doing came nearest in the classical period to the modern thesis of the man-machine. Because the Epicurean tradition spanned several centuries, itsteachings underwent much change from the founding of atomism in the fifth century by Democritus, through its continuation under Epicurus (ca. 341-270 B.C.), to the time of Lucretius (ca. 95-50 B.C.), in whose De
rerum natura a synthetic presentation of its philosophy has been preserved. As regards the atomistic prefiguration of the man-machine, it will suffice to summarize the Lucretian version.

The soul, like all else in the universe, was held to be a corporeal entity consisting of an assemblage of atoms. Those atoms which made up the soul, however, were of an extreme fineness comparable to the intangibility and mobility of air (pneuma), fire, or heat; in consequence they permeated the whole body. Soul and body therefore remained constantly in a state of mutual dependence by virtue of physical contact. While the soul-atoms did not separately possess life, consciousness, or sensibility, these attributes of the organism were the outcome of their appropriate combinations. From the Epicurean standpoint, all psychic phenomena were envisaged as the effects of specific (even if as yet ill-defined) atomic structures. The operations of the various senses and the faculty of sensation itself were explained on the same basis. It was supposed that all objects emit simulacra of themselves composed of a subtle grouping of atoms,

and that these replicas on entering through the related sense-organs impinge upon the soul as sensations and idea. It followed that the conscious and thinking principle in man was mortal, and that the age-old belief in personal survival after death was an illusion. The soul temporarily forming with the body a composite in which the role of each was essential to that of the other, this reciprocity ended with the destruction of the body and the dispersal of the soul-atoms. The absolute material unity of man was thus affirmed—a unity which made of death a simple physical event in the cycle of aggregations, dissolutions, and re-aggregations of the eternal atoms. The general picture of man that emerged from Epicurean philosophy was that of a momentarily coherent system of particles, of which both the internal motions and the interactions with a natural environment produced, by fundamentally mechanical means, not only the phenomena of life and sensibility that were common also to animals, but the higher mental functions believed to be peculiarly human. Atomistic speculation contained within itself, at least virtually, the seeds of modern science, including as an offshoot of the latter the man-machine. When the moment for the birth of that idea was to become ripe many centuries later, the inspirations and precedents offered by Epicureanism were to be put to important use. But it must be admitted that ancient atomism itself fell short of a genuine mechanistic conception of mind. It was prevented primarily by its own abstract postulates about the nature of matter from representing the organism in terms of its observable structures and processes. One detects still in the image of the soul as a diffusion of atoms within the body something of the earliest doctrines that identified the Greek pneuma and the Latin anima with breath or air, in the naïve materialism typical of the origins of thought on the subject. The persistence, however much transformed, of such primordial intuitions in the Epicurean hypothesis of ethereal soul-atoms, which served to exclude in theory a truly physiological approach to the mechanics of vital and psychic phenomena, was a reflection, moreover, of the poverty of anatomical knowledge in antiquity—a situation resulting from the religious ban against dissections of the human body.

Not only was medicine of little help here, but what existed as a science of mechanics in the same period was also unable as yet to offer any schematization of the laws of motion which might have led the Epicureans to suppose that the organism was, rather than a vague and fortuitous assemblage of atoms, an actual machine of a definite type. The handicap of inadequate scientific data was compounded by the curious fact that classical atomism, although it laid the foundations for the future of physical inquiry, remained itself singularly indifferent to the objective truth or error of the particular theories it framed about the “nature of things.” It failed to see in its anticipation of the man-machine a starting point of scientific study. The paramount aim of the atomistic definition of soul, as of all Epicurean physics, was ethical. In furtherance of this, what counted was the type of explanation offered, rather than the detailed form it took. The ethical aim of Epicurean physics being to reassure its followers about the hazards of life, this was believed best attainable by banishing from the world the arbitrary intervention of the Gods. The fatalistic belief in the soul’s mortality was comforting because death, or rather the punishments to follow preached by religion, ceased thereby to be a source of dread. To induce the ataraxia, or peace of mind, of the sage, one atomistic theory, provided it was credible, was obviously as good as another. Thus the earliest approximation of the man-machine was taught as an antidote for the superstitious terror of the supernatural powers presumed to control human destiny. Its antireligious emphasis accounts for the vigorous suppression of the Epicurean idea of the man-machine, along with the entire philosophy of which it was a facet, once the official triumph of Christianity took place; for the new faith was less tolerant of its critics than many a paganism had been.

The idea was not to rise again to the surface and pursue its career until the resurgence of pre-Christian modes of thought in the seventeenth and eighteenth centuries. When that was to happen, the underlying tension between religion and the man-machine conception was also to be revived, until the latter idea was to mature finally into a full-fledged doctrine, a refutation of Christian dogma about the spirituality and immortality of man’s soul.

If Epicureanism supplied the materialist world view that later nurtured the man-machine, it was from a different source in Greek thought—from the Hippocratic school and its descendants—that the specifically medical background of the idea first came. The theory of the four humors, which was to enjoy so durable a vogue, attempted to explain the behavior of the mind, particularly as manifested through personality-types, in terms of physiological causes. Indebted, seemingly, to the “four elements” of Empedocles and to the prevalent taste for microcosmic-macrocosmic analogies, the treatise De natura hominis of the corpus Hippocrat-
icum, dating probably from the second half of the fifth century B.C., worked out a scheme of correlations between the preponderance in the body of blood, yellow bile, black bile, or phlegm, and the respective predominance of the character-traits of sanguinity, biliousness, melancholy, or apathy. Gross and fanciful as this system of causes and effects was, the real value of “humoralism” proved to be the scientific method and medical philosophy it exemplified. By assuming that mental states were regularly dependent on bodily conditions, it made this dependency a crucial object of further investigation and therapeutic practice. As an adjunct to its humoral doctrine, the Hippocratic school held also that climatological and other factors in the natural environment acted upon the temperament by way of the body, thereby producing variations of aptitude and mentality among individuals.

In the ultimate impact of ancient medicine on the formation of the man-machine, the role of Galen (129-ca. 199) was no less important than that of Hippocrates. Not only did Galen organize the medical knowledge of his day into a vast corpus, but his own contributions to it were such as to strengthen notably the link between humoralism and an incipient man-machine attitude. While retaining and developing the theory of the four temperaments and their related psychic classifications, he laid the groundwork for a physiology of the nervous system by being the first to demonstrate experimentally that the brain was the point of origin of the multitude of nerves which controlled, by specific functions, the various vital, sensory, or motor activities of the body. To explain how this control was effected physically, Galen launched on its long and adventurous career the hypothesis of “animal spirits” composed of that invisibly rarefied fluid supposed to be contained in the imagined tube-like hollow of the nerves. Man was seen, consequently, as an organism regulated in its operations by a definite organ, the brain, which, thanks to the animal-spirits of the nervous network, mechanically received sensory messages from all parts of the body and sent back its voluntary or involuntary commands. In this Galenic model, of which the combined humoral and neurological aspects tend to construe man as a sort of hydraulic-pneumatic machine (reflecting in Greco-Roman times the privileged status of water-technology and the popularity of the pneuma-concept of soul), we have already the rudimentary structure that in fact unifies body and mind into an organic entity. On the basis of it, Galenism foreshadowed a materialistic picture of man, even though the philosophical opinions of its founder remained eclectic and, on the particular problem of the soul, loyal to Platonic and Aristotelian assertions of its substantial immateriality. But the soul, in so far as it came under the double dominion of the humors and the brain, was no longer treated as an independent being, but rather as something so fatefully bound up with the body that medical science was held to be the most effective means of regulating the passions, and thereby of remedying character-disorders. By proclaiming the interdependence of corporeal, moral, and mental states in the interests of a therapeutic ideal, Galenic teaching approached the threshold of the man-machine idea during the classical era—a fact that La Mettrie’s l’Homme machine was going to appreciate. It is important, furthermore, to recall that the Hippocratic and Galenic traditions, in contrast to the ideological suppression of Epicureanism, remained in authority without interruption until the seventeenth century, and were thus able historically to exert, at the right moment, a maximum influence on the maturing of the man-machine, at least to the extent that the latter idea had major roots in medical thought.

It remains, finally, to relate how the man-machine was prefigured in the achievements of ancient technology; that is, to what degree the latter succeeded in simulating animal or human behavior by mechanical means. The inventiveness of antiquity was applied, on the whole, to machines for lifting or pulling heavy weights (pulleys, winches, cranes, levers), engines of war (catapults, siege and defense equipment), pneumatic and hydraulic contrivances (water-clocks, fountains, pumps, water-organs), presses of various kinds, and similar instruments of relatively simple design and operation. Truly automatic devices were rare and, when encountered, belonged mostly to the class of toys and other objects intended for amusement or entertainment, rather than to that of machinery for useful work. Among the reports of such gadgetry that have come down to us, surely the most remarkable deals with the “automatic theatre” of Heron of Alexandria (second half of the first century A.D.), who was perhaps the most versatile mechanist of the Greco-Roman period. The theater in question, as described in his treatise Peri Automatopoietikes, featured a five-act tragedy based on the legend of Nauplius; it was performed with the appropriate dramatis personae, scenery changes, sound effects, etc., all of it automatically controlled by a system of strings, reels, cogs, and levers attached to a motor consisting of a counterweight that descended slowly and uniformly. The technological virtuosity of Heron of Alexandria apparently did not, however, have any philosophical meaning for his contemporaries. It may, for one thing, be said to have come too late, when the gift for original speculation had largely spent itself. But in a broader sense, the triumphs of Greek engineering attributed to such figures as Ctesibios, Philo of Byzantium, and Heron remained outside the main stream of science. Even the genius of Archimedes (d. 222 B.C.), whose generalization of certain laws concerning the equilibrium of bodies had intimated the modern synthesis of geometry and physics, proved to be an isolated case, and failed to inspire the following that his methodology deserved. Because the Greek imagination in science was typically theoretical in temper rather than given to contriving machinery, there was something abortive, or at least markedly premature, in the discoveries of an Archimedes and in the inventions of a Heron of Alexandria, each of whom exhibited in his way a strong technomechanical bent.

To make clearer why “machinism” did not become a philosophical perspective in antiquity, it should also be stressed that the mechanical arts and everything pertaining to them were regarded as inherently too base for such a purpose. Philosophy, chiefly aristocratic in outlook from its inception, was concerned primarily with contemplative or ideal pursuits. Nor did the passion for mathematics in the Pythagorean and Platonic schools favor, as it has in modern times, the fusion of philosophical and technological modes of thought, because as a rule the mathematicism of the Greeks remained “pure.” Behind these attitudes it is evident that there was in operation a pervasive sociological factor, which would have rendered the man-machine idea “unthinkable” even if (contrary to what was actually true) all of its logical and technical components had already been given. Mechanical devices fell within the department of the artisan, many or most of whom were, in fact, slaves. The introduction of related concepts or criteria into philosophical thinking would have signified to the Greek intellect its own “enslavement”; for the unconscious equivalent of the man-machine, had such an idea been somehow proposed, would have been the slave himself, in the sense that the slave was quite literally man reduced to a machine. By the same token, it is not merely fortuitous that the rise of the man-machine doctrine will coincide, in the eighteenth century, with two causally connected revolutions, the one technological, the other socio-democratic.

To summarize, the man-machine was principally approached in classical thought from three different but converging directions: that of atomistic materialism and its extensions in biology and psychology; that of medical psychophysiology, as best seen in the Hippocratic and Galenic schools; and that of the technology pertaining to automata. These three approaches had not yet found, however, the synthesizing mind capable of bringing them effectually together; for not only were the materials made available by each of them still insufficient to that end, but the sociocultural climate (which participates in the shaping of even the most abstract notions) was such as still to exclude the possibility of man’s self-image as a machine.

The man-machine idea remained in abeyance during the period of almost twelve hundred years when the reigning Christian ideology checked or suppressed whatever in the philosophical heritage of the past remained unassimilable to its own position. The mechanistic conception of human nature was, of course, incompatible with theological dogmas affirming the spirituality and immortality of the soul and picturing man as a creature of God endowed with free will. It was not until the sixteenth century, when long repudiated aspects of Greek thought were revived, that a naturalistic view of man was reinstated. This first resulted at Padua from the reinterpretation of Aristotle. Reappraising from a medical standpoint Aristotle’s texts in the original, the Paduan criticism, especially Pomponazzi’s and Zabarella’s, had the double effect of rendering the spiritual permanence of the soul undemonstrable by reason, and of redefining the faculties of the “sensitive” and “intellective” soul as functions of the “material form” of the body. The work of Pomponazzi shows that Aristotelian metaphysics had the potential of yielding an essentially naturalistic psychology, to the extent that its key-concept of form could be made to coincide with the structure itself of the organism, that is, with anatomical and physiological data. That such a development was at least a possibility in the career of the man-machine idea is attested by the fact that, when La Mettrie’s Histoire naturelle de l’âme (1745), inspired by medical materialism, gave a preliminary theory of man, it did so in the context of a scholastic metaphysics suitably construed for the purpose. Nevertheless, the role of Peripateticism in the evolution of the man-machine remained quite modest.

The reason was not only that Italian naturalism had relatively little impact beyond the Alps, but also that the imminent revolution in science stemming from the physico-mathematical method was soon to be consummated against, and stubbornly resisted by, those claiming to be faithful to Aristotle. Therefore, a new and opposing philosophy, meant to legitimatize a physics concerned with formulating quantitatively the observable laws of motion, would henceforth serve as the conceptual framework for the man-machine. The mechanization of nature, which found its most systematic and far-reaching rationale in Cartesian thought, was the decisive step in the intellectual process that led finally to the mechanization of man himself. That process, however, was strongly helped by several events in science and technology during the sixteenth and early seventeenth centuries. Among the most important was the rebirth of anatomy, particularly under the impetus of Vesalius’ epoch-making De
humani corporis fabrica (1543). The modern mind thereby became familiarized with the image of the human body as a neat and exact assemblage of related structures—an image made all the more incisive by progress in the techniques of anatomical representation. Thus the inevitable analogy between the internal organization of the body and that of, say, a clock was first a common fact of visual experience. Harvey’s discovery of the circulation of the blood (ca.1616) was another occurrence of the same type. It furnished the missing key to the dynamics of what now appeared more than ever to be a hydraulic machine: the organism was not only arranged like a clock, but it “ticked” like one, with its mainspring simply a pump.

The task which thereafter devolved on physiology was to explain, consistently with the mechanics of circulation, the subordinate mechanisms of muscular movement and of sensory as well as motor impulses. To these permutations in man’s self-perception should be added the emergence of a technological ideal no less revolutionary than the rest, already heralded before 1500 by the remarkable vision of Leonardo da Vinci. The resolve to conquer nature and make it serve man—a theme that Bacon and Descartes soon elaborated philosophically—was in time, along with the retreat of occultist schemes of domination, to focus on the machine as the specific weapon of conquest. In the seventeenth century, it is true, the machine was still seen as no more than a means to an end; there was no question yet of a process of assimilation, technologically conditioned, between it and man. But the passionate use of a particular means modifies, in addition to the end it serves, the agent whose destiny becomes inseparable from its use. At the historic moment when technological mastery of nature became a methodically conscious goal, the idea of the man-machine was predictable by a general law of cultural change, according to which man comes eventually to resemble the instrumentality of his ambition and power.

It was Descartes’ definition of the animal as an automaton that initiated the modern phase of the man-machine. Although a similar opinion had been voiced as early as 1554 by the Spanish physician Gomez Pereira, it had no noticeable effect until it reappeared as part of the Cartesian philosophical reform. French thought from Descartes to the Enlightenment thereby became the theater in which the concept of automatism was by degrees generalized from the animal to man. The bête machine doctrine had resulted from Descartes’ metaphysical dualism. Once given the sharp distinction between a thinking and extended being (res cogitans and res extensa), it was patently less absurd to banish animals collectively from the realm of thinking substance than to have to distribute “rational souls” to them from the ape down to the flea. But more than a case of metaphysical expediency, the animal-automaton served also to illustrate positively the universal mechanism of matter. As the biological counterpart of Cartesian physics, it was a theoretical culmination of the iatromechanical current which had already become widespread in the medical sciences of the first half of the seventeenth century.

The meaning of the beast-machine as a physiological postulate can best be understood by viewing it in the light of its human equivalent sketched in the Traité de l’homme, where Descartes, as if momentarily forgetting his dualist position, seemed on the verge of recognizing in man, too, an automaton. Historically, the bête machine proved to be (contrary, no doubt, to what its author intended) simply a minimal and preliminary version of human automatism. In the long run the animal acted as a mediator between the machine and man—a service which early attested the projection from animal to human nature that has since become a commonplace of biological and psychological research. That the mechanistic emphasis of Descartes’ physiology threatened to undermine his metaphysics by inviting a transformation of the beast-machine into the man-machine, can be seen clearly from the description of organic functions given in the Traité de l’homme (1664):

… all the operations which I have attributed to this Machine, such as the digesting of food, the beating of the heart and arteries, nourishment and growth, respiration, waking, and sleeping; the reception of light, sounds, odors, tastes, warmth, and other like qualities into the exterior organs of sensation; the impression of the corresponding ideas upon a common sensorium and on the imagination; the retention or imprint of these ideas in the Memory; the internal movements of the Appetites and Passions; and finally, the external motions of all the members of the body… I wish that you would consider all of these as following altogether naturally in this Machine from the disposition of its organs alone, neither more nor less than do the movements of a clock or other automaton from that of its counterweights and wheels… (Oeuvres, Pléiade ed. [1953], p. 873).

The above passage shows that the technological models with which Descartes equated the “organic machine” were of a rather inept sort. The clock (which Aquinas had long ago compared to the motions produced in animals by instinct and appetite) was to remain, nevertheless, the seventeenth century’s favorite example of an automatic device simulating intelligence. Descartes had in mind also analogies offered by the hydraulically operated automata in the royal gardens of Saint-Germain, which the Traité de l’homme alluded to in order to explain how sense-perceptions activate the brain:

External objects which… determine [the corporeal machine] to move in various ways according to how the parts of the brain are disposed, are like strangers who, on entering some of the grottos where those fountains are found, themselves cause without being aware of it the movements that take place before their eyes: for they cannot enter without stepping on paving stones so arranged that, for instance, if they approach a bathing Diana, they will cause her to hide behind some shrubbery; and if they attempt to pursue her, they will cause to come towards them a Neptune brandishing his trident… (ibid., pp. 814-15).

There is evidence that Descartes, seeking experimental proof of his automatist doctrine, designed a little robot that could perform somersaults on a tightrope. Although such examples might well suggest that his sense of the imitative powers of mechanism was naively exaggerated, it is unlikely that Descartes regarded clock-like automata as reproducing in a literal fashion the far more complex and versatile behavior of animals. Ultimately, his notion of the beast-automaton was deduced from the general mechanism of nature, while the actual models proffered in support of it were merely the best that the technology of the period could provide.

Cartesian biology pictured the living organism—not unlike the universe of whirling vortices (tourbillons) which enclosed it—as basically a hydraulic machine. The activity of the nervous system, patterned on that of the vascular circulation, was explained by supposing that the nerves contained a rarefied fluid—i.e., the animal spirits (Esprits animaux), made up of the finest blood-particles—which, propelling itself back and forth between the brain and the periphery of the body, controlled all sensory and motor functions. To this hydraulic scheme Descartes added a thermodynamic feature by assuming that the heart operated on heat; and also, as his most promising contribution, he imagined a primitive form of reflex mechanism to account for involuntary muscular movement. The modern idea of the man-machine came into being largely as a result of the development that the animal-machine and the physiological science related to it underwent in common. The final outcome had indeed been foreseen in Descartes’ own time, and gave rise to objections against his view by various critics, some of whom went so far as to accuse him of heresy and of abetting materialism. In the “Sixth Objection” to the Méditations métaphysiques, a group of theologians claimed that the beast-automaton would lead its supporters to conclude that the continuity in intelligence between animals and human beings was attributable simply to machines of differing levels of complexity. This rejoinder was repeated often by opponents of the bête machine, who thereby unintentionally bestowed a measure of popularity, and even plausibility, on the very inference that they were eager to avert. The problem of “animal soul” became the subject of endless controversy, lasting well into the next century, between Cartesians and anti-Cartesians. While in one sense such metaphysical polemics for or against the animal-machine could only have proved futile (for it is impossible to know if any creature other than man is endowed with what we experience inwardly as res cogitans), in another sense it helped indirectly to render the automatist thesis more acceptable. This came about in several ways. Those who sought to refute Descartes on the grounds that beasts often exhibit, by their skill and cunning, a degree of intelligence equal and occasionally superior to that of human beings, were in effect citing evidence that could boomerang against them. For when the man-machine philosophy was at last proclaimed, its exponents—with La Mettrie at their head—could argue that if animals, despite their alleged merits, were mere machines, there remained no reason to suppose that human abilities implied a loftier kind of causation. The adversaries of the Cartesian doctrine, relying on scholastic tradition, also proposed a “corporeal soul,” situated midway between materiality and spirituality, as the specific principle of feeling and intelligence in animals. But the notion of “corporeal soul,” a derivative of the Aristotelian “substantial forms,” was logically inconsistent, and in the end, encouraged some to identify it more conveniently with the organic machine itself. That, at any rate, was what La Mettrie did in his Histoire naturelle de l’âme, in which Peripateticism, with reminiscences (as noted) of Pomponazzi and the Paduan school, became an ingredient of the materialistic definition of soul. Those Cartesians, moreover, who took up the cudgels for the bête machine were obliged to explain, in ever more ingenious detail, how merely mechanical processes could be the source of all the amazing variety of animal actions. In so doing, they freely introduced Descartes’ principles of psychophysiology into the subject of animal automatism, with the result that the mechanistic interpretation of psychological phenomena, at least in animals if not yet in man, crystallized as a general practice.

To the above developments should be added the curious vogue that the beast-machine enjoyed in certain religious circles, especially among the Jansenists. Far from regarding it as heretical, the latter, represented by their leading thinker, Arnauld, were fascinated by the automatist concept, discovering in it (as Descartes had intimated) a number of theological advantages. Not only did it set in a brighter light the dogma of a separate and transcendent destiny for the human soul, but it absolved men (and God) of blame for the sufferings erroneously believed to be inflicted on innocent beasts. More important still, it attested to the infinite art and wisdom of God, who had contrived such marvelous automata capable of imitating intelligent behavior. This excursion of the animal-machine into the sphere of natural theology was, in particular, to offer a dubious precedent which played eventually into the hands of the free-thinkers. For it followed that, if God could create such remarkable automata as animals were acknowledged to be, there was no need for him to do anything more, in creating man, than to improve on the mechanical models already in existence. The man-machine idea will thus ironically find theological support in the assertion that it is impious to consider the Supreme Artisan incapable of fashioning a machine as complicated and as admirable as man.

Although the animal-soul debate was concerned mainly with the question whether beasts were or were not pure automata devoid of feeling and thought,

Descartes’ own position had in reality been more nuanced and even somewhat ambiguous. In denying a soul to animals, he had meant only that they were without rational awareness—an opinion confirmed empirically both by the “unreflecting” efficiency of their actions and by their lack of the linguistic means needed for the formation of abstract ideas. This signified that the animal, unlike Descartes, did not perform intellectual operations of the type cogito, ergo
sum; but its inability to cogitate did not necessarily deprive it also of all nonreflective kinds of mental activity, such as simple consciousness, memory, emotion, and perception. Descartes conceded to the beast, in fact, a level of psychic life directly dependent on its physical organization. The extension of the bête
machine doctrine, so understood, to the behavior of man by those Cartesians, prone to naturalism, who saw in it above all the opportunity to explain psychological phenomena mechanistically, had its initial logic in Descartes’ over-restrictive definition of the soul as a purely rational substance distinct from all else in the universal mechanism where it was so tenuously lodged.

The proposal to investigate within the machinist context, first in the animal and subsequently in man, such “sub-rational” faculties as sensation, memory, imagination, feeling, and volition, oriented the future program of psychophysiological science and thereby set the stage for the maturing of the man-machine idea. Among those who notably caused Cartesian thought to evolve in this direction, Henricus Regius, professor of Medicine at Utrecht, gave to the automatist thesis, in his Fundamenta physices (1646), an interpretation which, neglecting dualist metaphysics, stressed the conformity of psychic processes with their organic counterparts. Jacques Rohault’s Entretiens sur la philosophie (1671) followed Descartes in denying to animals a rational soul, but thereupon proceeded to examine the remaining aspects of their conscious life in terms of those mechanical structures assumed to be the basis of the vitality and sensibility which they manifested.

In a similar exposition of the bête machine, Pierre Sylvain Régis (Système de philosophie, 1690) had as his purpose not so much to deprive animals of attributes commonly included under the designation of their “soul,” as to demonstrate that those same attributes were owing to “the arrangements of their organic parts alone, and to the heat of their blood and the force of their animal-spirits.” In this physiologizing inheritance of Cartesian natural science, the animal-spirits in particular were soon to have a privileged role, namely, as the innervating substance believed to engender and sustain the higher functions of the brain. Some advanced thinkers all but substituted this substance for the soul itself.

Thus the progress of physiology tended to minimize the “ghost” which Descartes had found it metaphysically necessary to introduce into the “human machine” of the Traité de l’homme. An inherent contradiction of dualism had been the supposed interaction between a substance that occupied—indeed was—space and a substance—thought—that was essentially nonspatial.

Given the impossibility of discovering the laws of such an interaction, there could be no science of the cause-and-effect relations between body and mind in accordance with Cartesian principles. Descartes’ own attempt to solve the problem by assuming that the soul was housed in the pineal gland, where it acted like a brake-man switching the incoming impulses of the animal-spirits in one direction or another, can only be considered futile in view of both the neurological fantasy and logical inconsistency that it displayed. Indeed, dualistic psychology led into a blind alley. The attempts of Leibniz, Malebranche, and Spinoza—each of whom was concerned to overcome within the framework of dualism the dilemma posed by Descartes’ unintelligible parallelism of mental and bodily functions—did not in the end forestall the solution of the dilemma that was forthcoming from the man-machine philosophy. If Leibniz’ pre-established harmony, Malebranche’s occasionalism, and Spinoza’s monism vindicated, each in its way, a metaphysical modality of the mind-body correspondence, none of these explanations was of any special use in determining empirically the laws which governed that correspondence.

As it turned out, the impasse of dualism seemed to be circumvented best by the increase in knowledge of the central nervous system, and particularly of the cerebral localization of specific functions. The result of such advances in physiology (which by La Mettrie’s time had arrived at a rough differentiation of the types of activity peculiar to the cortex, cerebellum, and brain-stem, as well as at the stage of a comparative neuro-anatomy of man and several animal species), was the gradual replacement of the unlocatable soul by the brain itself, which came to be seen as a “machine” producing thought. The long-run sterility of dualism as a psychological hypothesis—for it could only lead either to a gratuitous dichotomization of its human subject, or to the introduction of a nonfunctional soul into the unity of body and mind—caused it at length to be abandoned by certain unorthodox thinkers in favor of the man-machine hypothesis, which by contrast had the advantage of recognizing the concrete nature of man as that of a being in whom mental and physical events were never divorced from one another. The triumph of mechanistic psychology cannot be understood, however, without taking fully into account the influences exerted on it, often in an eclectic manner, by the overlapping currents of Hobbism, Lockean empiricism, and Epicureanism in the intellectual setting of the early eighteenth century. In the De homine (1658) of Hobbes, there was already outlined, contemporaneously with the Cartesian postulate of automatism, a complete rationale for the mechanization of mind.

Inspired by the new physics, Hobbes was the first to reduce all things to nothing but bodies in motion; and since for him only efficient causes were real, psychology and epistemology became branches of mechanics like any other science of nature, except that imperceptibly minute motions were said to be involved in the entry of sense-impressions into the brain. Psychic phenomena were thus conceived essentially as “a motion in the internal substance of the head.” The grossness of Hobbesian materialism, coupled with the anti-experimental and deductive method that supported it, limited somewhat the historical importance of its precocious version of the man-machine theme. While there was no hesitancy on its author’s part to describe man abstractly as a machine, the scientific motive for imagining specific analogies between mechanism and organism was lacking in Hobbes’ reliance on physico-mathematical generalities. Nevertheless, his contribution was valuable especially because of the linkage it effected between the mechanics of sensation and an empirical theory of knowledge. In following to its conclusion this epistemological lead, the materialists of the Enlightenment will succeed in “mechanizing” the homo duplex of metaphysical tradition. The immediate ground of this final step, however, proved to be the empiricism of Locke, who far more than Hobbes shaped their thinking. Once the procedure to refer mental and emotive states to the organic dispositions that accompanied them had become well established, it seemed logically and psychologically appropriate to combine this unification with a consistent sensationalism. Approaching Lockean epistemology with a marked materialistic bias, La Mettrie and those who followed him achieved between empiricism and mechanistic biology a synthesis which eliminated all recourse to an immaterial principle in analyzing how the mind acquires its ideas.

In this outcome, the role of Gassendi, who championed an empiricism of Epicurean stamp, paralleled and soon merged with that of Locke. Moreover, Gassendi’s revival of the atomistic definition of sensitive soul as a rarefied, fiery substance was easily assimilated to the mechanistic physiology then prevalent, serving to reinforce the opinion that psychic activity resulted from the flow of Esprits animaux back and forth between the brain and the sensory apparatus.

Such a combination of automatism, atomism, and empiricism is well seen in the case of Guillaume Lamy, a professor of the Paris Medical Faculty, who as early as 1678 anticipated the man-machine in his Explication
mécanique et physique des fonctions de l’âme sensitive,
ou des sens, des passions et du mouvement volontaire.

But in the trend to materialism which thus drew sustenance from a broad spectrum of sources, the importance of Spinoza as a catalyzing agent should not be neglected. It was mainly in Spinozism that La Mettrie and a number of philosophes found, as part of what they took to be a naturalistic and atheistic metaphysics, the key notion of necessity which they consolidated with the man-machine idea, arriving at a doctrine of mental and moral determinism that made of free-will a mere subjective illusion.

All the attitudes and influences discussed above made their least inhibited appearance in the free-thinking literature that circulated privately in France after 1700, and in which different approximations of the man-machine may be said to have enjoyed at first an “underground” existence. The idea was originally propagated, therefore, as a salient feature of the radical critiques aimed at the official ideology of the Ancien
Régime. In this initial phase of its career, the incipient man-machine idea had predominantly an antireligious and subversive meaning, and was regarded rightly, on the whole, as dangerous to social and political institutions by the defenders of tradition and authority, who sought, though ineffectually, to suppress it. Among the many examples of such a use of mechanistic psychology are to be found the revolutionary Testament (1729) of the notorious apostate priest, Jean Meslier, and, in the class of anonymous works extant in manuscript, L’Ame
matérielle and Essai sur les facultés de l’âme.

It was not, however, until the publication of La Mettrie’s L’Homme machine (1747) that the idea provocatively epitomized by its title was at last affirmed as the basis and focus of a coherent philosophical position. From profusely cited evidence of what he took to be an invariable correlation between mental and physical states in the individual, La Mettrie concluded that, in addition to every vital and involuntary function, all the forms of conscious life—such as sensation, the passions, memory, thinking, volition—are regularly contingent upon the “organic machine,” and more exactly on the structures and activity of the central nervous system. Characteristic of this viewpoint was the fact that its author, himself a physician who had been a disciple of the leading iatromechanist, Hermann Boerhaave (1668-1738), gave it as the gist of a materialist philosophy that remained closely responsive to the methodology, scope, and aims of the medical sciences. As a result, while his advocacy of the man-machine still retained numerous antireligious, polemical, or propagandist traits, it had the originality of being put forward primarily as a general heuristic hypothesis for the scientific study of behavior. La Mettrie eschewed, as far as possible, its metaphysical implications (whether positive or negative) in regard to the ultimate nature of matter and mind, or of the causality underlying their mechanistic union. He thereby succeeded in harmonizing the experimentalist ideal of modern science, which had only recently come to the fore in France, with his main thesis. The man-machine was held to be a logically valid notion not because it expressed any apriorist truth about human nature, but on the strength of induction from verifiable psychophysical data. Consistently with this, La Mettrie was fond of analogies that pictured the mind as a “thinking and feeling machine” into which ideas, entering as coded symbols, were not merely stored, compared, and combined, but were also continuously colored and modified by emotive and instinctual messages flowing into the same centers of perception. The goal of psychology, according to the man-machine hypothesis, became the gradual clarification in detail of the complexities, admittedly limitless, of this cerebral process—a goal which, La Mettrie believed, held out the best hope of diminishing the enigma that man posed both generically and individually.

Although he stated that his doctrine was simply that of the beast-machine drawn out to its final consequences, actually La Mettrie’s use of mechanism as a biological concept represented an important advance over the Cartesian view of the organism as essentially like any man-made, artificially actuated device. In contrast to such a “dead mechanism” approach, La Mettrie sought to describe the vital machine with which man was equated as a dynamical and self-sufficient system typified by an internal finality. “The human body,” he wrote, “is a machine that winds its own springs—the living image of perpetual motion”; and more organismically: “man is an assemblage of springs that are activated reciprocally by one another, without it being possible to say at what precise point

of this human circle nature has begun.” This conception was only in part inspired by technological achievements. The favorite criterion of an “intelligent” machine, in the eighteenth century as in the seventeenth, continued to be the ordinary clock, alongside which La Mettrie placed, however, the harpsichord as a model for the epistemological mechanics of registering, composing, and reproducing ideas like so many musical notes played on the cerebral “chords.” Special mention deserves to be made also of Vaucanson’s automata, the most ingenious of the period, which had in fact been contrived as practical simulations of different biological processes. There was among others his famous “duck,” which could paddle itself about, and “digest” food by means of a stomach that substituted, as might be expected, mechanical for bio-chemical operations. But while the homme machine clearly profited from such scientific interests, it rested on more specifically biological grounds. La Mettrie referred the capability of automatic reactions which the organism possessed to the reactive energy manifested in a concrete way by the key-phenomenon of irritability. He thus saw in the property of muscle-tissue irritability, which Haller had recently discovered and illustrated experimentally, the vital force responsible for the purposive dynamism peculiar to physiological, as compared with merely physical, machines.

In most quarters, the man-machine philosophy was angrily denounced as a dangerous paradox, first, because it offended peoples’ religious sentiments or deflated their vanity (which La Mettrie fully intended); but it was even more offensive because of certain implied moral conclusions. Claiming in his Discours
sur le bonheur (1750) that happiness was a mental state dependent essentially on somatic conditions, La Mettrie divorced the “supreme good” of man from the practice of traditional virtues, and redefined it primarily as a medical rather than an ethical question—a reversal which, taken together with his readiness to relieve even criminals of the “disease” of guilt and remorse, struck his contemporaries as an immoralist’s cynical defense of vice and anarchy. The usefulness of La Mettrie’s deterministic—hence amoral—psychology is, however, far plainer to us now than it was to his own century. The man-machine idea had the merit of bringing to the age-old problem of the moral perfectibility of man a whole new dimension, consisting in the ability of medicine to act upon the mind, emotions, and personality by variously modifying their underlying organic causes. La Mettrie may be said to have introduced into the sphere of general ethics a set of criteria inspired by medical humanitarianism, and supported by the psychiatric evidence that man’s behavior is not in fact as free as it is commonly held to be.

Since La Mettrie, almost all materialist philosophy has subscribed in one form or another to the man-machine (even if the term itself, doubtless owing to its shock value, has never been popular). The leading advocate of the idea later in the eighteenth century was Diderot, whose versatile genius provided a nuanced and rich context for its development. He brought out, especially, its organismic potential by differentiating three structural levels in the human machine—that is, the elementary “cellular” units, the individual organs, and the organism as a whole—and by placing at the apex of their integrated operations the various manifestations of psychic life. Assuming, furthermore, that there was in nature an indeterminate number of “molecules,” endowed with latent sensibility, which coalesced according to fixed laws, the Rêve de D’Alembert (1769)—which would remain unknown until the next century—sought to trace, with a gift for mechanistic analogies that was as much literary as scientific, the emergence of life, consciousness, sensation, the passions, memory, and reflection in terms of the ascending complexity and functional continuity of the related organic structures. More than this radical morphologizing of the man-machine, Diderot was the first to present the latter within the framework of a general transformistic theory embracing the history of all the animal species, with the outcome that man was perceived not merely as a machine, but as one that had been slowly constituted in time by the same universal laws of moving matter that governed his present behavior. The man-machine thereby found a suitable place in the system of evolutionary materialism that Diderot expounded in a largely hypothetical and conjectural vein. It was in his work, moreover, that the modern socioeconomic overtones of the idea first began to appear, although still indirectly, alongside its far more obvious antecedents in biological and medical science. When seen in relation to the enormous importance that Diderot ascribed, in the Encyclopédie, to the machinery and techniques of the manufacturing arts, the man-machine idea would appear to have been on the verge of a new significance. In his dual effort to mechanize man and to humanize technology, there was implicit a coextensiveness of the man-machine with the nascent reality of an industrial world, in which man was to be described at length not merely as himself a machine, but as the creator and master of countless other machines that would be objectifications of himself and, as it were, his “offspring.” Diderot thus succeeded in evoking the broader implications, both biological and techno-social, of the man-machine; but no less clairvoyant was his sense of the basic contradictions between an impersonally mechanistic and deterministic view of human nature and man’s inward awareness of freedom in choosing the moral, artistic, and affective values essential to his experience. The probing treatment, in a fictional work such as Jacques le fataliste, of this dilemma posed by Diderot’s equally deep commitment to a humanistic and to a scientific vision of things, served in the end to point up a permanent paradox at the core of existence itself.

Among other versions or near-versions of the man-machine in the fertile eighteenth-century milieu, the physiological psychology of David Hartley should be noted. Influenced by Newton’s theory of the ether no less than by Newton’s reduction of the multiplicity of physical events to a single principle, Hartley’s Observations on Man (1749) proposed to interpret all mental phenomena as resulting from vibratory motions in the brain and nerves—a hypothesis that had the great advantage, in his eyes, of accounting for the mechanics of the “law of association” by which all ideas were assumed to cohere. Although his associationist psychology, unlike the man-machine doctrine, preserved a formal distinction and parallelism between body and mind, Hartley did not hesitate to apply his vibration-principle in a comprehensive and deterministic fashion; he thereby represented the organism in general on the model of an elastic machine in which the impact of external events generated the specific vibratory responses that were the biological basis of every variety of psychic event.

A different and more limited use of the man-machine idea may be found in the two treatises of Helvétius: De l’esprit (1758) and De l’homme (1774). Conceding the premiss that “Man is a machine which, once set in motion by physical sensibility, executes all its acts necessarily,” Helvétius elaborated a rigidly environmentalist theory of education by way of explaining the enormous variations among individuals. The corrective to this one-sided method came, however, with Diderot’s Réfutation d’Helvétius, in which it was argued that a psychology aiming to be at once materialistic and sensationistic must consider as a variable, not only the total environment in which each mind develops, but the organism that underlies and informs its development.

In the writings of Holbach, the man-machine took a militantly atheistic turn. His Système de la nature (1770) made it the starting point of an intransigeant, rather reductive materialism, which, beyond its vehement anticlericalism, had positive ethical and political goals. The Holbachian man-machine served, more precisely, as the psychological complement of a “natural morality” derived from the pleasure-principle and consistent with the rule of social utility. This he opposed sharply to the “unnatural,” spiritualist morality imposed by the Christian religion, and called for a radical reform of the political institutions of the Ancien
Régime in the name of the felicity to which man, as a physical being, was logically entitled in this world.

Finally, in the major contribution of Cabanis, Rapports du physique et du moral de l’homme (1795), the culmination of eighteenth-century interest in psycho-physiology may be witnessed. Convinced no less than La Mettrie, Diderot, or Holbach of the primacy of the organic machine, he combined this approach in extensor with the method by which Condillac and Helvétius had already furnished a descriptive analysis of the role of sense-perception in the formation of ideas. In a well-known passage, Cabanis pictured the brain as an organ that produced thinking in the same manner that the stomach digested food, adding: “We conclude that the brain somehow digests sense-impressions, that it effects organically the secretion of thought.” Contrary to this rather blunt formula, he worked out the details of his psychophysiology in a methodical and thorough way, laying special stress on such factors as age, sex, temperament, diet, physical exertion, occupational pursuits, pathological conditions, the use of drugs and stimulants, climate, and so forth. As in La Mettrie, the theme of “physiological salvation” loomed large, supported by the broad responsibility that Cabanis granted to medical science in the improvement of the human personality. On the other hand, it must be admitted that Cabanis referred only summarily to the actual mechanistic character of the organism, and, if anything, chose to play down the man-machine equation during the post-Revolutionary years when it was linked in public opinion with the ideological excesses that atheistic materialism was accused of having promoted.

In retrospect, the career of the man-machine idea during the Enlightenment may be said to have consisted of two phases. Up to about 1740, the concept of mechanism with which physiologists remained imbued was too rigid and narrow to offer, except in isolated instances, plausible models for the organic behavior it pretended to interpret. Beginning with the 1740’s, however, a profound shift took place in biological speculation, exemplified by such figures as Buffon, La Mettrie, Diderot, and Maupertuis, the effect of which was to bring into sharp focus precisely those qualities of living things that would strike later generations as vitalistic rather than mechanistic in character. This reorientation of interest did not, as might have been expected, bring about the rejection of the established modes of explanation; instead it resulted in a new tendency to conceive of the mechanical with a degree of flexibility and imaginativeness sufficiently great to allow the inclusion of vital phenomena within the compass of loosely mechanistic hypotheses. To be sure, the notion of mechanism, in such a stretching of definitions, no longer corresponded to the rigorously geometrical method of the Cartesian school. By a seemingly paradoxical, but in reality merely transitional step, the mechanistic biology of the second half of the eighteenth century ceased to be mathematical in spirit, and even sought to transcend, with an attitude of deliberate antimathematicism on the part of Diderot and Buffon, the authority of classical mechanics, which was now felt to be, however philosophically valid, futile and stifling in a technical sense. Inevitably, the commitment to mechanistic principles or models among such biological-minded philosophes as La Mettrie and Diderot had something vague and suppositional about it; what it gained in suggestive visual power, it lost (at least temporarily) in analytical clarity and quantitative precision. The truth is that the century which invented the man-machine disposed as yet of very modest means for inferring biological, to say nothing of mental, processes from what was reliably known about the behavior of the inanimate world. The meaning of the man-machine idea, as propounded by La Mettrie or Diderot, was therefore above all an affirmation of scientific faith—an appeal addressed to posterity—concerning the ultimate fecundity of the mechanistic method in bridging the gap between the living and nonliving, and between the conscious and unconscious, aspects of a presumably unitary nature.

It was in the Enlightenment that the man-machine idea may be said to have attained optimum expression, aided by the pre-Revolutionary thrust of materialistic and atheistic attitudes. But even then its success extended only feebly beyond the borders of France to countries such as England and Germany, where intellectual loyalties remained conservative. In the first half of the nineteenth century, moreover, the vogue of idealistic philosophy and introspective psychology, under the sway of romanticism, forced a broad retreat of the man-machine thesis. From this temporary eclipse the latter will gradually work its way up again to a new kind of prominence by the end of the century, under the influence of scientific developments favorable to it. Despite its final vindication, the man-machine will never quite regain its past authority as a systematic principle. It has survived since the eighteenth century mainly as an essential element—or often as a basic tendency—present either explicitly or implicitly in various configurations of thought in those disciplines that have contributed most to its growth. Owing to this changed historical status of the question, it would seem unprofitable henceforth to treat the man-machine idea sequentially. Rather, its fortunes will be assessed in relation to pertinent progress in the fields of biology, physiology, psychology, technology, and philosophy.

Such a procedure is all the more fitting because of the differentiation that the sciences themselves underwent during the nineteenth century in the course of their emancipation from “natural” and “mental” (or “moral”) philosophy. Following this specialization of the methods and goals of research, the man-machine came to have significantly different applications and meanings for each of the branches of knowledge in which it enjoyed a vested interest. The advances in neurology proved specially germane to the resurgence of the idea. Charles Bell’s (1774-1842) discovery of the dual character of the nervous system served to clarify the distinction between efferent and afferent impulses, thus preparing the ground for a comprehensive and exact investigation of reflex action. The work of Claude Bernard (1813-78) on vascular reflexes and on the regulatory role of the sympathetic system was a forward stride for the man-machine, because it showed experimentally that the viscera, by direct or indirect links to the brain, were able to produce bodily changes affecting memory, perception, emotivity, and thinking. In fact, the general elucidation since the early nineteenth century of the varieties of reflex mechanism, together with the more recent extension of the principle to the Pavlovian conditioned reflex, has demonstrated in detail how far specific forms of conscious activity proceed from the integrated automatic play of the nervous apparatus.

The perfecting of “neuron theory” led simultaneously to a better understanding of the nature of neural conduction and of psychophysical dynamics. To these discoveries should be added, of course, the accumulation of data concerning the problem of cerebral localization. From the pseudoscientific “cranioscopy” of Franz Joseph Gall (1758-1828), through the crucial researches of Pierre Flourens (1794-1867) on the behavior of decorticated pigeons, to the tentative brain-topography sketched from clinical observation of various motor and sensory types of aphasia, the nineteenth century offered increasing evidence for the belief that the central nervous system was the adequate and controlling instrument of mental life. Such a conclusion was supported, moreover, by what histological analysis revealed in regard to the association-patterns of fibres and the functional stratification within the brain. Nineteenth-century philosophy mirrored or confirmed, albeit in a minor key, the standpoint of human machinism. It was favored by Comtean thought to the extent that the latter insisted, as against introspective or speculative approaches, on the value of a positivistic method in psychology which, in the historically given circumstances, could only lead to the primacy of the physiological factor. The current of materialism that came to the fore in Germany around the mid-century, represented by figures such as Feuerbach, Vogt, Moleschott, Czolbe, and Büchner, took for granted the validity of the man-machine conception. In England, Spencer’s “Synthetic Philosophy,” although not actually materialistic, did not hesitate to classify “mental science” as one of the natural sciences, with the result that in the Spencerian hierarchy of the sciences, psychology mediated the transition from biology to sociology. G. H. Lewes (1817-78), rejecting the dualist separation of mind and body, held that “sentience” was a mechanical process peculiar to animate beings, out of which, under the appropriate conditions, consciousness in all its degrees developed. Hippolyte Taine (1828-93), who was inclined to view man as a “nervous machine” and to define thoughts and feelings deterministically as products not unlike sugar and vitriol, applied his psychophysical theories to literary criticism; while, under his aegis, Émile Zola and the naturalists sought to illustrate through the medium of fiction that individual fate was the inexorable outcome of hereditary and environmental forces.

Physiological psychology as a special branch of science flourished under the stimulus of the aforementioned interests. In the period roughly from 1830 to 1860, the group of German experimentalists which included J. Müller, Virchow, Helmholtz, Du Bois-Reymond, and others, made remarkable progress in the study of the physiology of sensation and perception. Rudolph Hermann Lotze’s (1817-81) Medizinische
Psychologie, oder Physiologie der Seele (1852), a prototype of many similar treatises, was proof that the viability of the man-machine idea did not narrowly suppose monistic or materialistic convictions; for its author, although a philosophical idealist and occasionalist, regarded the nervous system as a pure mechanism in his discussion of it as the basis of mind. A.

Horwicz (Psychologische Analysen auf physiologischer
Grundlage, 1872-78) studied emotion as the somatically conditioned source of consciousness and of psychic life in general. T. Ziehen’s Leitfaden der physiologischen Psychologie (1891) affirmed, among other things, that there was no real distinction between voluntary and involuntary thinking, thus echoing the automatist theory propagated by the eighteenth-century materialists. These principles were expanded upon by H. Münsterberg (Grundzüge der Psychologie, 1900), who predicted that psychology would become an exact science only in so far as it utilized the unequivocal evidence furnished by neurophysiology. In England, too, there was a parallel tendency to explain the energetics and conduct of the mind in terms of its organic constituents, as attested by the work of A. Bain (The Senses and the Intellect, 1855) and by that of such exponents of the same school of psychology as T. Laycock (Mind and Brain, 1860), W. B. Carpenter (Principles of Mental Physiology, 1874), and Henry Maudsley, who plainly took the view (in Physiology
and Pathology of the Mind, 1867) that consciousness was a by-product of brain processes. In America, William James gave a large place to the physiological method in his investigation of behavior, as best seen perhaps in the James-Lange theory of emotion. A decisive factor in the long-run success of human machinism was Darwinian biology and the new orientations that it provoked in psychology. The hypothesis that man was descended from lower forms of life dramatically weakened whatever presumption was still left that his origins and nature had a spiritual, transcendent dimension; and in the same proportion it reinforced the axiom that all human characteristics were natural phenomena admitting of natural explanations. It was consistent with evolutionist logic to explain the diverse levels of psychic capability in man as direct correlates of the ascending order of complexity and differentiation that the selective struggle for existence had wrought in his organic endowment. The continuity thus established between him and the higher animal species was an invitation to study human beings by the same behavioral criteria, rooted in biologically given instincts and needs, that were appropriate (and indeed inevitable) in the study of animals.

The combined impetus of the developments in science and philosophy that have been briefly summarized was responsible for the reemergence of the man -machine doctrine at the start of the twentieth century with the sort of intellectual respectability that it had clearly lacked in its eighteenth-century version. Its restored vitality involved, of course, several qualifications of its meaning and scope. The new man-machine did not signify any simple or self-apparent equation between human nature and man-made mechanical devices a fact which indicates why the idea itself caught on much better than La Mettrie’s rather offensive sounding name for it). On the contrary, the machinery of the body was now seen as an enormously complex self-adaptive system of a physicochemical type analyzable into molecular structures, for which, moreover, no faithful analogue could be cited among artificial machines. The man-machine therefore affirmed only that the dynamics of organism must ultimately be governed by the same laws that governed mechanical systems—an assumption in methodological agreement with the twin principles of simplicity and the unity of science. In its psychological and philosophical reaches, the idea has come to mean that psychical events, at least in theory, are empirically attributable, according to specific, regular, and determinable patterns, to neural mechanisms, without it being obligatory to define, whether a priori or a
posteriori, the underlying causation or the ontological status of mind.

Since around 1900, the man-machine has been a pervasive idea in the three disciplines—namely, biology, psychology, and philosophy—among which its career and promise continue mainly to be shared. In each case, however, it has come to have a different sort of relevance. In the biological sphere, the ever more exact clarification of the physicochemical processes of the organism—and of the electrochemical properties of its nervous component—has had the cumulative effect of justifying the experimental procedures and theoretical standpoint of the “mechanists.” Nevertheless, the status of the man-machine remains contingent upon the centuries-old, still unsettled controversy between vitalism and mechanism. An episode in that debate which might seem pertinent here occurred when E. Rignano published Man Not a Machine,
A Study of the Finalistic Aspects of Life (1926), and was promptly refuted by J. Needham’s Man A Machine,
in Answer to a Romantical and Unscientific Treatise (1928). The vitalistic contention that the organism, while admittedly a physical system, cannot be understood in terms of the same fundamental laws exemplified by the behavior of inorganic mechanisms, remains tenable as long as living things cannot be synthesized in the laboratory, despite the methodological sterility and diminishing plausibility that may be reproached against it. The thrust of vitalism, at any rate, has been to deny that man is accurately describable as a machine, apart from the question whether his psychic being is or is not a dependency of his body. Twentieth-century psychology, although it has been largely unconcerned with deciding if the brain works “mechanistically” or “organismically,” has in various other ways embodied or corroborated some form of the man-machine idea. The highly specialized interest in animal psychology initiated by John B. Watson and pursued by the behaviorists has lent weight to the man-machine by virtue of the uniformity it supposes between the more mechanical and predictable acts of animals and those, seemingly less so, of human beings. Thus, the comparison of man and animal under a single psychological perspective in our time has been an experimental reenactment of the speculative step which, during the seventeenth and eighteenth centuries, had already transformed the beast-automaton into the man-machine. More broadly, behaviorism has coincided with the standpoint of human mechanism in proportion as it has limited itself to observing the mind nonsubjectively from without, for such happens to be also the only way in which the behavior of a machine can be perceived and explained. Conversely, it is only the external or “public” behavior of a human being that the machine is able to simulate. To insist on a psychology restricted to behavior alone makes psychology, therefore, the science of machines no less than of animals or men. By excluding from consideration what is least amenable to mechanistic analogies—that is, consciousness and subjective states—behaviorism has given a blanket endorsement to the man-machine.

In the case of Freudian psychology, it may be said that the blurring of the ordinary distinction between voluntary and involuntary actions as a result of the role of the unconscious, has corroborated the same idea by suggesting that conscious thoughts and desires are continuations, on a different plane, of those instinctual forces—in particular, the sexual—which manifestly originate in the organism. Psychoanalytic exploration of countless “unconscious mechanisms” has brought to light and catalogued a whole new province of “automatisms” in the life of the psyche. The primacy of instincts (or “drives”) arising from the biological makeup of the animal or human being has been the standpoint, similarly, of the purposive psychology associated with the names of McDougall and Tolman.

While its various exponents have differed over the degree of physiological determinism involved, the theory of “drive” has generally been useful to the man-machine doctrine by providing a sort of nexus for mechanistic and motivational accounts of psychodynamics. Hull, moreover, has stressed the neurological basis of motivation to the point of asserting the isomorphism of cerebral and mental structures, and of envisaging a science of psychology guided by the homeostatic principle. This science of man would be deducible (at least hypothetically) from physiological postulates about stimuli issuing from the external and internal environment of the organism, and from inherited neural connections between receptors and effectors. Köhler has realized, in the attempt to explain visual perception, a synthesis of Gestaltist and mechanistic hypotheses by the extension of physical field theory to cerebral functioning. No less significant for the man-machine position, however, has been the impressive advance of psychophysiology itself in our era. The role of endocrinological factors, although perhaps overestimated a few decades ago, has, nonetheless, been fitted conspicuously into the overall picture of how the body controls the mind. The importance of glandular determinants is reflected in the human typologies that Kretschmer and Sheldon have worked out by means of statistical correlations between personality and physique. Continuing research, aided by new techniques of localization, has greatly perfected the functional topography of the brain, particularly in regard to the roles of the mid-brain and brain-stem, as well as their patterns of integration with one another and with the cortex. But these technical contributions, while strengthening the presumption in favor of the man-machine, also remain problematical. For example, the investigation of “projection areas” and their interchangeability of function has made it more difficult than before to imagine an exact isomorphism between mind and brain, or to suggest actual mechanical models for how the latter performs its task. At the same time, all of the available psychophysical knowledge can explain no more than the general features and grosser aspects of the organic basis of mind. The infinite diversity that individual thoughts, feelings, and actions exhibit still remains quite unrelated in any verifiable sense to specific neural traces or processes.

In contemporary philosophy, the status of the man-machine is inseparable from the mind-body problem. Many philosophers would now concede both that the organism is reducible to the same laws operative in all nonorganic systems, and that mental events cannot exist except as the consequences of neural events. But the real problem lies elsewhere; because if, in the man-machine formula, biology has been concerned mainly with the term “machine,” and psychology with the term “man,” the essential concern of recent philosophy has become the hyphen connecting the two terms. The decline of dualistic, monistic, and materialistic doctrines founded on the concept of substance has set the validity of the man-machine thesis in an entirely different key. Logical positivism has led Carnap and Neurath to the view that meaningful statements about the mind are only those which refer to its outwardly observable properties and can therefore be tested. The epistemic form of materialism has in turn promoted, as best seen perhaps in the work of Wittgenstein and Ryle, a behavioristic analysis of mind, the general effect of which has been to construe “mentalistic” propositions as “physicalistic” proposi- tions. Such “reductionist” efforts to circumvent the perennial mind-body dilemma are tantamount to re-articulating the man-machine idea as a program of logical reconciliation between two separate universes of experience and of discourse. More radically consistent with the idea, however, is the “identity theory” of Feigl, Place, and Smart, which assumes a De facto, empirical identification of mental states or processes with states or processes of the central nervous system.

Nevertheless, certain difficulties persist. That every mental event has its specific causal counterpart in a neuromechanical event remains a merely hypothetical, and probably in practice an unverifiable, principle. As a result, the physicalistic method of analyzing the mind tends to interpret psychic reality in an idiom which, when it refers to neural processes, risks becoming gratuitously indirect and obscure, and, when it refers to public behavior, fails to express what is given phenomenologically in consciousness.

The advent of cybernetic technology has greatly added to the analogical force of the man-machine idea. The construction of numerous mechanical devices with purposive and self-adaptive characteristics has had, first, a decisive impact counter to vitalism, by showing that modes of behavior long held to be peculiar to living systems need not necessarily lie beyond the range of mechanism. Simultaneously, a whole gamut of intellectual capabilities, such as remembering, learning, judging, foreseeing, problem-solving, etc., have been simulated by information-fed machines that are able, among other things, to run mazes, prove theorems, compose music, play chess, translate from one language into another, and calculate with an efficiency unapproachable by the human mind. The design of these auto-regulated devices has suggested various useful hypotheses in neurophysiology and psychophysiology, especially as regards the mechanism of reflex action and the neural mechanics of analogous operations occurring in the brain. Cybernetics has thereby brought to the man-machine thesis a new dimension borrowed from electronic technology: notions such as “conductors,” “circuits,” “signals,” “relays,” “electric charges,” “thresholds,” “feed-back,” and the like, have gained currency in attempts to describe the performance of the central nervous apparatus. The corresponding model of man that has emerged is a composite of the earlier physicochemical machine and of a computerized guidance system present within it. While the influence on philosophy of such technological innovations has been obviously to bolster the postulate that mental events are somehow identifiable with neuro-mechanical events, in other respects the contribution of cybernetics has been controversial and confusing. It has led, in particular, to the inverse formulation of the man-machine, that is, to what might be called the “machine-man” idea—a reversal of things which had, in fact, always been implicit in the original. Some philosophers have consequently chosen to deal behavioristically with the “mentality” of machines by an ambivalent or metaphorical use of terms properly descriptive of human beings and animals. But the “thinking” in which machines engage is limited normally to predetermined operations that are, moreover, reducible to mathematical sequences. It is not easy to imagine a mechanical analogue of the brain that could faithfully reproduce the intertexture of all the types of thinking appropriate to all the situations that human beings confront, together with the nonlogical modes through which ideas are associated in the “stream of consciousness.” Even if such a feat of simulation were theoretically conceivable, there would be no technological means of imitating subjective reality. A kind of dualism thus attaches to mechanistic philosophy itself as regards the distinction between natural and artificial machines, the former manifesting a technologic of which consciousness remains the essential and non-duplicable trait.

Yet concern about the “mentality” of machines in contemporary thought is symptomatic of the sociocultural meaning that the man-machine has acquired in post-industrial societies on the threshold of automation. The technical superiority of the machine, by transforming mere efficiency into a human ideal, has set in motion a convergence between itself and man which tends, on the one hand, to lift the robot to a sort of sub-human role, and on the other, to assimilate man to the machine not only in the biological or psycho-physiological sense, but also in relation to his values and conduct. Such an invasion of man’s private world by criteria typical of automata has provoked, understandably, a reaction which raises the problem of how far his nature may be equated with that of the machine. The golem, which in sixteenth-century Yiddish folklore was envisaged as a beneficent servant of man, has spawned in our own time a numerous progeny of “mechanical creatures” about whose intentions we are far less confident. The obsessive leitmotiv, so popular in science fiction, of human civilization being threatened by a robot takeover, would seem thus to betray symbolically a widespread fear of the automatization of life; for the menacing robot rival is actually man himself perceived in a depersonalized future shape.

In conclusion, the man-machine idea may be said at present to occupy a strategic and fateful position at the confluence of several disciplines and traditions: in neurophysiology and psychology it is above all a fecund empirical hypothesis of indefinite promise to research; in philosophy, it is a speculative option in the attempt to resolve the body-mind problem; in technology, it expresses the demiurgic goal of mastering our environment by the mechanical maximation of our limited powers; and as a theme in sociology and the imaginative arts, it most often conveys the malaise of dehumanization in modern culture, and conjures up fantasies that put in doubt the survival of man’s authentic self.


George S. Brett, History of Psychology, ed. R. S. Peters (London, 1962; New York, 1963).

John Cohen, Human
Robots in Myth and Science (London, 1966; South Brunswick, N.J., and New York, 1967).

Gunderson, Men-
tality and Machines (Garden City, 1971).
Heikki Kirkinen, Les Origines de la conception moderne de l’Homme-Machine (Helsinki, 1960).

A. Lange, The History of Materialism (New York, 1950; original German edition, 1865).
Leonora C. Rosenfeld, From Beast-Machine to Man-Machine: Animal
Soul in French Letters from Descartes to La Mettrie (New York, 1941).

Aram Vartanian, Diderot and Descartes: A Study
of Scientific Naturalism in the Enlightenment (Princeton, 1953); esp. Ch. IV; idem, La Mettrie’s L’Homme Machine:
A Study in the Origins of an Idea, critical edition with an introductory monograph and notes (Princeton, 1960).

The translations for Descartes are by the author of the article.

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