I recently just finished reading Julien Jean Offray de La Mettrie’s L’Homme Machine and have come away with a surprising appreciation for this 18th century French materialist philosopher. Originally published in 1747, La Mettrie’s philosophical treatise argued in favor of classical materialism instead of Cartesian dualism in seeking to explain the human species. The major underpinnings of La Mettrie’s argument are both his full embrace of the philosophical works of John Locke and the medical science of his day.

One of the primary hallmarks of Cartesian dualism was the belief that human beings were composed of two distinct substances: a thinking substance (res cogitans) or soul and a physical material substance (res extensa). It is important to first note before proceeding that during this period res extensa/body/material matter was thought to comprise of extension, however, this is not how modern physicists think of material matter today, which is why I dub La Mettrie a classical materialist. In fact, as Noam Chomsky is apt to point out, there has not been a coherent notion of material matter since Sir Issac Newton dismantled René Descartes’ framework of it with the publication of Philosophiae naturalis principia mathematica in 1687. What set human beings apart from the rest of the animals, as Cartesians argued, was the fact that humans have this res cogitans while animals do not. For the Cartesian philosophers, animals were just extremely complex machines without minds/souls.

La Mettrie rejects the Cartesian notion of res cogitans and argues that human beings are just as much an animal as any other. This is not to say that the mind/soul (L’Esprit / L’Ame), which should not be confused with the brain, does not exist. Rather, La Mettrie argues that the mind must be based upon physical/materialist principles. In short, all animals, including humans, have minds, but that these minds originate from material substances, not from a separate thinking substance (res cogitans). In order to prove his argument, La Mettrie looks for causation of not only mental events, but also bodily events. One such example is the thought experiment of the French king getting agitated for being in the cold. This is because, La Mettrie argues, the French king has not been raised in a cold environment. However, for those who have been raised in a cold environment, they would not be caused such discomfort.

In a more radical experiment, La Mettrie proposes that someone take a young monkey and place it within an urban human setting under the tutelage of a human tutor. The tutor is then to raise the monkey as though it were a human child. La Mettrie argues that the monkey, due to its intense similarities with human beings, would inevitably learn human language for thinking and profiting its own education. Clearly to modern day people, such a proposition is patently ridiculous. Monkeys do not have the mental capacities to do such feats.

Concerning motion itself, La Mettrie points to several medical experiments of his day whereby motion occurs in separated body parts and organs. In one experiment, he details the prodding of muscles which causes them to contract, and another where a human heart is tossed into a fire, whereby it begins to bounce. For La Mettrie, these experiments demonstrate that there is no need for a thinking substance or soul to cause motion. The body parts themselves move, albeit due to outside material forces.

He makes similar arguments concerning ideas and thought themselves. Following in the footsteps of Locke, La Mettrie believes that all ideas are generated due to the inputs of external factors via sensations and the processing of such by thought. This leads him to say:

La plus belle, la plus grande, ou la plus forte imagination, est donc la plus propre aux Sciences, comme aux Arts. Je ne décide point s’il faut plus d’esprit pour exceller dans l’Art des Aristotes, ou des Descartes, que dans celui des Euripides, ou des Sophocles; et si la Nature s’est mise en plus grands frais, pour faire Newton, que pour former Corneille, (ce dont je doute fort;) mais il est certain que c’est la seule imagination diversement appliquée, qui a fait leur différent triomphe et leur gloire immortelle.

The most fine, the most grand, or the strongest imagination is just as well exposed to the sciences as to the arts. I have not decided if it is necessary for the most excellent mind to excel in the art of Aristotle, or Descartes, than in the arts of Euripides, or Sophocles; and [whether] if Nature has placed more effort in forming Newton than in forming Corneille, (which I strongly doubt); but it is certain that only the imagination diversely applied has forged their various triumphs and immortal legacies.

Julien Jean Offray de La Mettrie, L’Homme Machine, 30 (FB Editions)

In short, exposure to new ideas and elements is fundamental to a good education, although one might quibble with La Mettrie’s staunch Lockeanisms. Despite these staunch proclamations of materialism, La Mettrie is eventually forced to concede the limitations of his theory insofar that he doesn’t fully account for thought. His theories offer the explanatory power as to how thought works, but he doesn’t explain why thought exists at all.Towards the end of his work La Mettrie says concerning the matter of thought:

Je crois la pensée si peu incompatible avec la matière organisée, qu’elle semble en être une propriété, telle que l’Electricité, la Faculté motrice, l’Impénétrabilité, l’Entendüe, etc.

I believe that thought is so little incompatible with organized material, that it seems to be a property of material matter such as electricity, motor faculty, impenetrability [due to the property of extension], hearing, etc.

Julien Jean Offray de La Mettrie, L’Homme Machine, 48 (FB Editions)

In the end, while La Mettrie feels that he has divested res cogitans of some of its most central elements of simplicity and centrality, he recognizes that there are still some aspects of it that he has not explained. However, whereas a Cartesian might seek to use this mystery to justify the existence of res cogitans, La Mettrie holds out the hope that one day it might fully be explained in materialistic terms. In some sense, La Mettrie’s hope is very similar to the modern thesis proposed by some cognitive neuroscientists: that things mental arise from brain states.