More than a few notable philosophers have been doctors. Four that come to mind are Locke, Hartley, Lotze, and William James. Locke’s medical services to Lord Shaftesbury got him started on his public career as ideologist-in-chief to the Whigs, who wanted to exclude James II from succeeding his brother Charles II on the throne of England. Hartley was the associationist thinker who was such an object of veneration to Coleridge that the poet named his first son after him. Hermann Lotze was much respected by the British Hegelians of the late nineteenth century, who had all his writings translated. William James’s achievement is well known. Aristotle was, like Helvétius and Humphrey Bogart, the son of a fashionable doctor, but not a medical man himself. He was, however, biologically minded, believing that to understand the real nature of anything one must grasp what it is striving to become and asserting the continuity of all varieties of life: vegetable, animal, and human. All of these philosophers, with the exception of Lotze, but including Aristotle, were naturalistic, rather than spiritualistic, Hartley to the point of materialism and Locke approaching it.

Julien Offray de La Mettrie (1709–1751) was perhaps the most intensely medical and the most materialistic of all doctor-philosophers. He was trained in Paris and Rheims, studied under the great Boerhaave in Leiden, served as surgeon to the royal guard, and contributed to the study of smallpox, dysentery, and vertigo. He was not all that progressive in some of the details of his practice. He was in favor of bleeding and opposed inoculation for smallpox. In the history of medicine he has left only the faintest trace. His name does not appear, for example, in the gigantically comprehensive history of the subject by Arturo Castiglioni or in the well-known shorter history of Charles Singer.

Kathleen Wellman, in her solid, lucidly written, somewhat pedestrian book, argues that the materialistic and unedifyingly hedonistic philosophy for which La Mettrie is best known—a scandal to his contemporaries and an embarrassment to the philosophes among them—was a direct continuation and fulfillment of his medical interests. These were expressed in the first instance at an institutional level, in the form of a series of vigorous satires directed at the leaders of the medical profession in France. At the time his career began, physicians, who were only a fifth as numerous as the surgeons, were tightly organized to make the most of the benefits of their monopoly position in the medical world. Surgeons—the “physicians of the poor”—combined their medical undertakings with the practice of barbering. With wigs becoming fashionable, the two trades drifted apart from each other, leaving surgeons proper free for upward social movement.

La Mettrie’s case against the physicians was not just that they exploited the sick by restricting entry into the profession. His main point was that the theoretical training they received in the ancient classics of medicine and which they saw as the basis of their preeminence was, in fact, useless and very often harmful. The surgeons learned by experience, on the job, whereas the physicians applied themselves to their patients, equipped only with traditional and ill-founded lore about humors and the like. Surgeons, taking their cue from Harvey’s discovery of the circulation of the blood, studied anatomy; physicians studied Latin texts. Physicians disparaged surgeons as ignorant of Latin and incapable of reasoning. To La Mettrie the inherited theory on which they prided themselves was no more than vacuous metaphysical speculation. In its place he called for a Baconian medical science, founded on experience, not abstract first principles, and with a definite practical aim.

La Mettrie’s first philosophical book, L’histoire naturelle de l’âme, came out in 1745. It is a more conventionally presented treatise than any of his later writings but not a model of rational organization. It is principally directed against Descartes’s doctrine of the substantial soul, the inscrutable something or other which ties our individual mental states together and the possession of which differentiates human beings from everything else in the universe. In the same way as Locke, La Mettrie holds that the soul is no more knowable in its essence than the body. What we actually know about both is what we can observe them to be or do. He invokes Aristotle against Descartes, the Aristotle who held that the soul is the principle of vital movement and activity of plants, animals, and men, and not something capable of existing independently of them. He claims that motion is intrinsic to matter, not imposed from outside by some kind of miraculous divine push.

Following Locke again in seeing all the contents of the human mind as derived from sensation, he is more emphatic than Locke about the fundamentally material nature of sensation, which is the effect of physical causes that excite physical responses in the brain and nervous system by way of physical sense organs. Descartes’s extraordinary doctrine that animals have no feelings, that they are machines in the sense of being wholly devoid of sensations, he rejects as absurd. We have as much reason to think that animals have feelings as that human beings other than ourselves do. In the first place there are the likenesses between their behavior in similar circumstances. Then there are the considerable anatomical correspondences between humans and animals to be taken into account.


L’Homme machine (1748) carries on the materialist program of showing the mind to be part of nature by accumulating instances of mind-body connection. Kathleen Wellman rightly points out that La Mettrie’s title can easily be misinterpreted. He is not saying, under the influence of some prophetic inspiration, that the brain is a computer. Spread about his writings are allusions to such facts as the effects on memory of injuries to the brain, the likeness of our basic motives of hunger and love to those of animals, the mental aspects of sleep, eating and drinking, and bodily illnesses.

In the later book he is concerned to tackle the last defensive redoubt of dualism: the conception of reason, the peculiarly human part of the soul, as entirely nonmaterial, whatever may be true of the “lower” mental functions—sensation, emotion, desire, memory, imagination, and so forth. He identifies reason, supposedly distinctive of the human species, with the power of speech. It is not all that distinctive, since animals can communicate. He conjectures, anticipating Washoe, the calculating chimpanzee, that it might be possible to teach an ape to speak. A stronger argument is that human beings cannot always have spoken and must have developed their linguistic competence in the course of evolution. The use of language, he maintains, is rooted in the imagination. That, understood in the style of Hobbes and Locke as “decaying sense,” is evidently bound up with the body. Generally his tactic is to draw the boundary around the supposedly nonmaterial element as tightly as possible and then to argue that even this is inextricably tied to what is without question bodily.

After L’histoire naturelle de l’âme La Mettrie retired to Holland, but even that comparatively liberal community found L’Homme machine too much to bear. So he moved to the court of Frederick the Great at that hospitable monarch’s invitation a year before the arrival of Voltaire. Unlike Voltaire, he did not quarrel with his host. In the year of his hedonistic Art de jouir, 1751, he died at the age of forty two, after eating some pâté, or, perhaps, a pâté des truffes, which had gone off. Enemies put it about that, in accordance with the voluptuary principles of conduct he proclaimed, he had died of overeating. A number of medieval English kings used to be said to have died of “surfeit.” But, in an age without refrigerators, salmonella is more likely than gluttony.

One of the best accounts of La Mettrie is the chapter devoted to him by F.A. Lange in his great History of Materialism (1866). Lange says of La Mettrie that he is “one of the most abused, but one of the least read, authors in the history of literature.” He only just makes his way into the history of philosophy. Kathleen Wellman, who makes no mention of Lange, remarks that La Mettrie is treated in a perfunctory way by historians of the Enlightenment on a large scale such as Paul Hazard, Ernst Cassirer, and Peter Gay. He does not do much better in histories of philosophy, though there are reasonable short accounts in the works of Windelband, Hoffding, Gopleston, and J.H. Randall, Jr.

Those who do pay attention to him make the point that, active in the first stages of the French Enlightenment and dying in the year of publication of the first volume of the Encyclopédie, he had a number of important ideas before anyone else. He was the first categorical materialist among the philosophes, preceding, and probably influencing, d’Holbach, whose Système de la Nature came out nearly twenty years after La Mettrie’s death, and Diderot, whose avowal of materialism in his Entretien entre d’Alembert et Diderot, written in 1769, and his Rêve d’Alembert were not published until after his death in 1784. Lange says that La Mettrie asserted the unity of all organic life before Buffon. He was one of the first modern evolutionists, although he had no explanatory mechanism to suggest, no hint of Darwin’s great idea of natural selection winnowing out random variations. He anticipated the modern theory of a primeval soup as the source of life in remarkably similar language; in his case it was elemental mud. He thought criminals were sick and ought to be treated, rather than punished.


La Mettrie’s obscure place in the history of thought must be caused in part by the uncomfortable, even scandalous, nature of his ideas. He was an atheist at a time when his intellectually progressive contemporaries were calling a halt at deism. He was an outright materialist at a time when Locke’s mildly materialist followers in England—Hartley and Priestley, for example—were tentatively tracing out the consequences of his parenthetical supposition that “it might have pleased God to attach the power of thinking to material substance,” while remaining, in the spirit of that remark and Locke’s own example, believers in God. Atheism and Materialism were bad enough. La Mettrie’s hedonism was really too much.

People beginning the study of philosophy are often a little disappointed to find that thinkers of the past who are described as hedonists turn out to be thoroughly tame and respectable. Epicurus, for example, did not recommend the riotous flinging of roses. His ideal of life was to sit about in a garden with some friends having an intellectual discussion and drinking a prudently watered glass of wine. The earlier Aristippus of Cyrene was bolder. What was of highest value for him was positive pleasure, not the defeatist summum bonum of later antiquity: the absence of pain. He stressed, in particular, the supreme value of present, bodily satisfaction, although he qualified this first principle by saying that the wise pleasure seeker will take account of the possible painful consequences of his actions.

La Mettrie’s moral philosophy is much like that of Aristippus. In opposition to the deeply rooted Platonic-Christian conviction of the unimportance or valuelessness of straightforward bodily pleasure, he applauded it. It is often intense and it is available to everyone. It is much more solid than phantoms like honor. The happiness of intoxication is as real as any other. What is more, the much trumpeted sources of higher pleasure—knowledge and culture—are more peripheral to the nature of man than the fundamental impulses of hunger and love which he shares with other animals, and they are often harmful. Reason has a place in the organization of one’s pursuit of pleasure. He draws a distinction between volupté, pleasure pure and simple, and débauche, the kind of pleasure that brings with it suffering, whether bodily pain or social disapproval. For there is a social dimension to La Mettrie’s moral theory. We have to live with one another, and virtue consists in conduct which society—the state and public opinion—endorses.

Kathleen Wellman points out something which I have not seen mentioned anywhere else—that La Mettrie’s medically based conception of human nature does not take it to be greatly, let alone completely, malleable. For him l’éducation peut peu, where for Helvétius elle peut tout, an expansion of Locke’s view of the mind as a tabula rasa. Diderot drew on La Mettrie to resist the extremity of Helvétius’s environmentalism, but, like d’Holbach, made as little as possible of this debt to him. In a proto-Freudian spirit La Mettrie contends that society asks too much of individuals, in whom it inspires unnecessary and irrational remorse. At one point, indeed, he argues that remorse is altogether irrational, on the ground that it is wholly backward-looking, unlike that other great force for virtue, fear of the law. He ignores the consideration that remorse, to be genuine, must embody an intention to behave better in future. His medically nourished awareness of the persistence of individual human constitutions and of the differences between them leads him to an attractively breezy kind of tolerance, a realism about human nature that is untainted by edifying theory.

Two things in particular emerge from Kathleen Wellman’s useful study. The first is the overall coherence of La Mettrie’s ideas, which she persuasively attributes to his medical experience and interests. Treatment of the sick is likely to encourage a belief in the deep-seated dependence of the mind on the body, in the variety of individual constitutions, and in the limited responsiveness of these differing constitutions to external influences. Such considerations led him to be skeptical about his teacher Boerhaave’s optimism about the future prospects of medical science. The second is La Mettrie’s genial humanity and his tolerance for human variety, even in its most lamentable manifestations, his endorsement of simple human pleasures and his Lucretian concern to relieve people from metaphysical and superstitious anxiety.

Should he be more highly regarded as a philosopher than he has been? His writings lack the elegant logical articulation of those of the main target of his criticism, Descartes. They are not as long and detailed as the works in which d’Holbach, twenty years after La Mettrie’s death, was to present a similar view of the nature of things, in an altogether less sprightly manner. La Mettrie’s philosophical writings all fit into one dumpy little eighteenth-century volume of seven hundred pages and make agreeable reading.

For one piece of reasoning, at any rate, he ought to be honored: his refutation of Descartes’s ludicrous thesis that nonhuman animals are automata. Arnauld had raised the matter in his objections to Descartes’s Meditations and had been put off with a footling answer. Descartes was led to his view about animals by his radical distinction of the contents of the universe into two, and only two, utterly different kinds of thing: the mental or conscious and the material or extended. It follows from this that the nonrational or subrational parts of the mind—feelings, emotions, desires, and so on—are, since they are items of consciousness, nonphysical. (Most types of mental content, except perhaps sensations and images, are rational to the extent of being thought-impregnated, although they do not involve reasoning. Anger, for instance, involves the belief that its object has harmed one.)

Descartes held that living bodies, animal or human, are pieces of purely physical machinery. In the case of human beings a spiritual substance or soul is inserted, temporarily, into one of these mechanisms. Why could he not have allowed animals to have a soul of an inferior, nonrational kind? The problem would then arise that, since this inferior conscious entity is still a substance, it would be indestructible, except by God, and so immortal. An alternative to the unpalatable implication of animal immortality would be to drop the questionable assumption that all substances are (naturally) indestructible. But that would undermine the best that Descartes has to offer in the way of an argument for the immortality of the human soul. Or again, he could have held that only the rational part of the soul is immortal, but immortality without memory, emotion, or desire seems hardly worth having. There is also the difficulty of showing animals to be nonrational, in the light of the large and inescapable evidence for their being intelligent.

All that is a problem for Descartes. What is not in doubt is that his conclusion that animals are unfeeling automata is absurd. When animals are hit they cry out and do not just withdraw like sensitive plants. Watering mouths and wide-opened eyes reveal desire and emotion in them as in us. We and they have eyes to see with, noses beneath them to breathe and smell with, mouths a bit further down to take in food and drink. Within their and our mouths are teeth to grind food into a form in which it can be swallowed and digested and tongues with which to taste it. And so anatomically on.

La Mettrie, arguing for the continuity of humans with animals, suggests that animals have a moral capacity since they suffer from remorse. Here he may have confused a reaction he favored with one he disapproved of: remorse with fear of punishment. Animals are certainly given to behavior that is in the interest of other sentient beings but that is not in their own interest, and are capable of self-sacrifice. If that is attributed to the evolutionary process of kin selection or to genetic imprinting, the same may be true of our own moral achievements.

What La Mettrie does not, I think, explicitly conclude from his ideas about the continuity between human beings and animals is that animals, like human beings, are proper objects of moral concern. Since animals are susceptible to suffering, as we are, they are part of the overall moral constituency. A recognition of the moral significance of animal suffering is, at the very least, wholly consistent both with La Mettrie’s philosophy and with his humane disposition. Materialism, which denies the superhumanity of the human race, is an impediment to inhumanity.

This Issue

March 25, 1993