Julien Offroy de La Mettrie

La Mettrie, Julien Offroy de (1709–51)

La Mettrie is best known as the author of the eighteenth-century materialist manifesto, L’Homme machine (1747). His interest in philosophical issues grew out of his preoccupation with medicine, and he developed a tradition of medical materialism within the French Enlightenment. Born in St Malo, into the family of a prosperous textile merchant, La Mettrie pursued a medical career in Paris. He also studied for two years with the renowned Hermann Boerhaave in Leiden. After a brief period of medical practice, La Mettrie devoted his efforts to his translations and commentaries on Boerhaave’s medical works. He also began to publish the works that made him a pariah to both the Faculty of Medicine of Paris and to the orthodox – that is, his medical satires and his first work of materialist philosophy, L’Histoire naturelle de l’âme (1745). Because of the outrage provoked by these works, he was exiled to Holland in 1745. But L’Homme machine, the text in which he applied his materialism thoroughly and explicitly to human beings, was too radical even for the unusually tolerant Dutch, and La Mettrie was forced to seek asylum at the court of Frederick the Great where he later died. His willingness to publish ideas his contemporaries considered too dangerous led the philosophes to repudiate him.

1 Medical roots of materialism

La Mettrie’s best known work, L’Homme machine (1747), has sometimes been construed, largely because of its title, as a simple application to man of Descartes’ bête machine hypothesis (see Descartes, R. §12). But his materialism is richer, less mechanistic, and more embedded in the scientific and medical traditions of the eighteenth century than this narrow appreciation has suggested.

La Mettrie’s interest in philosophical issues grew out of his preoccupation with medicine. His medical works include translations and commentaries on Boerhaave’s principal works, five medical treatises on specific diseases and public health, and seven volumes of medical satires lampooning the ignorance and venality of the medical profession. His work manifests the hostility to metaphysics and commitment to an empiricism typical of many medical writers in the eighteenth century. His awareness of the divergent manifestations of disease in different individuals led him to emphasize the importance of the physiological constitution in his philosophical works. La Mettrie built upon Boerhaave’s tentative correlations between Lockean epistemology and the physiology of mental process to develop a materialist philosophy. That is to say, he not only adopted Lockean psychology as the best framework within which to discuss brain functions but also made the easy transition from Locke to materialism; in all of his philosophical writings, he emphasized the physiological evidence for taking this step.

2 Materialist philosophy

La Mettrie’s first philosophical work, L’Histoire naturelle de l’âme (1745), appears to be a conventional metaphysical treatise in style and vocabulary. But he deliberately subverted conventional philosophical arguments to argue for materialism, perhaps attempting to legitimate materialism by placing it within the established philosophical canon (see Materialism in the philosophy of mind). For example, he claimed that Aristotelian substantial forms – defined as the power of matter to acquire form, force, and the faculty of sensation – prefigured his materialism. He used the Aristotelian sensitive soul as a fruitful way to discuss mental processes and cited, as an epistemological rallying cry, the Aristotelian maxim, ‘nothing in the intellect which is not first in the senses’. He wielded his materialist reading of Locke as a weapon against seventeenth-century metaphysicians, especially Leibniz and Descartes, to argue that the soul could be completely identified with the physical functions of the body and that any claims about its existence or function must be substantiated through physiology. Without the impediment to research and understanding that the notion of the immortal soul posed, one could come to a more realistic assessment of human nature by studying all available scientific data. Writing as a physician committed to the practical application of empirical physiology to investigations of human nature and the soul, La Mettrie reappraised philosophical issues with the evidence and methods of medicine and physiology.

In L’Homme machine (1747), La Mettrie adopted a freer and more polemical style to canvass all the scientific issues of his day for empirical evidence for materialism. He provided lengthy and elaborate discussion of the physical basis of human behaviour in order to demonstrate that the effects of the body on the soul are so striking that one cannot reasonably assume that a soul controls the body; thus one must ultimately conclude that the soul, if the term has any meaning, must be considered part of the body. He used evidence drawn from anatomy, physiology, and psychology to assert the complete dependence of the soul on the body. Albrecht von Haller’s findings on muscular irritability were particularly attractive to La Mettrie as the most conclusive evidence against those who refused to admit that matter was capable of selfmovement, particularly the Cartesians. Making no qualitative distinction between conscious and voluntary and involuntary or instinctual, La Mettrie posited an active, organic, and selfmoving ‘man machine’. With his materialist theory of man substantiated by physiological experiments, La Mettrie thoroughly compared human beings to animals, despite the implicit disparagement of conventional notions of man’s place in the universe which those comparisons entailed. Furthermore, he suggested that atheism was the logical outcome of his notion of an active, selfcreating and sustaining nature.

La Mettrie’s other works on the philosophy of nature, L’Homme plante (1748) and Système d’Epicure (1750), further integrate human beings in nature by comparing them to lower creatures, like plants, and by placing them in the context of the unfolding of matter and motion in an evolutionary process.

In these works, La Mettrie empowered the physician, at the expense of the theologian and metaphysician, because he maintained that the physician’s physiological understanding of human beings was the most sound and most likely to yield productive results. The close connections he was able to draw between physical and mental processes demonstrated the utility of knowledge gleaned by his method, which was unsystematic, incautious and unconstrained by standards of orthodoxy, bound instead by stringent empirical standards – the method, he suggested, of the reform-minded, empiricist physician. La Mettrie then turned his attention to an area where the authority of the metaphysician or the theologian traditionally prevailed over that of the physician, ethics.

3 Moral philosophy

La Mettrie’s Discours sur le bonheur (1750) used his materialist notion of man and his place in nature to examine the implications of materialism for moral systems and for the individual in society. He raised the question of the effect society can have on the individual or the degree to which education can countervail physiological determinants.

He sought to determine whether our notions of virtue and vice correspond to human nature as revealed by physiology. The evidence of comparative anatomy led him to conclude that society was not only unnatural but also arbitrary, and that its notions of virtue and vice, while socially useful, were fundamentally at odds with nature and simply the result of socialization. Therefore, just as the physician must acknowledge the effects of the individual constitution on health and disease, La Mettrie insists, so too must the moral reformer recognize the limits that the individual constitution imposes on one’s ability to behave in the ways society has defined as virtuous. The brunt of La Mettrie’s moral argument is the hope that society, recognizing that its notions of virtue and vice are relative and designed merely to further its interests, will be persuaded to reward a greater range of human behaviour; thus, more individuals will be able to aspire to social virtues. In light of his understanding of human nature and morality, La Mettrie critically appraised other moral systems; he indicted Christianity and Stoicism, in particular, for their distorted views of human nature (see Virtues and vices).

4 Role in the Enlightenment

La Mettrie was more pessimistic than other philosophes about the possibility of social reform; for him, reform efforts were severely circumscribed by the sway that the physiological constitution exercises over the individual. His specific claim that virtue and vice are completely relative put him at odds with the aspirations of other Enlightenment moralists writing within the natural law tradition, and his hedonistic ethic put him beyond the pale as far as many of his contemporaries were concerned. But despite the fact that virtually all of the philosophes, even those like Diderot and d’Holbach who were indebted to him, found it dangerous to be associated with his radical materialism, La Mettrie himself was eager to proclaim his adherence to them. In his last philosophical work, the Discours préliminaire, written in 1751 just as the philosophic movement was beginning to coalesce around the Encyclopedia, La Mettrie claimed to speak for the philosophes. He explicitly identified his work in both medicine and philosophy with their concerns for reform. Where medicine offered hope for a more naturalistic understanding of human nature, the médecin-philosophe (a term he coined) might be able to reform social institutions in accord with that understanding. La Mettrie’s medical materialism is his distinctive contribution to the French Enlightenment and the history of philosophy.