Person

Julien Offray de La Mettrie

French physician and philosopher (1709-1751), author of L'Homme machine (Man a Machine, 1747), the most notorious statement of materialism in the French Enlightenment. A student of the great Dutch physician Hermann Boerhaave, La Mettrie argued from medicine rather than metaphysics: because every faculty of the mind rises and falls with the state of the body, the soul is nothing but the organization of the body itself. His books were condemned in France and in Holland, and he ended his life under the protection of Frederick the Great in Berlin.

For apologetics he is the cleanest historical example of the position the Argument from Reason and the Argument from Consciousness are built to answer. He also presents a careful reader with a surprise: his own book does not deny God outright, and the first rebuttal it received came from the publisher who printed it.

Biography

• 1709, born at Saint-Malo in Brittany, the son of a prosperous textile merchant
• Studied in Paris and took a medical degree at Reims, then studied physiology and chemistry under Boerhaave at Leiden, whose works he later translated into French
• 1745, published Histoire naturelle de l'âme (The Natural History of the Soul); the outcry cost him his position and drove him to Holland
• 1747, L'Homme machine, published anonymously at Leiden by Elie Luzac; the first edition carries the date 1748. The book was condemned in Holland as well, and the same year saw L'Homme plante
• 1748, came to Berlin in February under the protection of Frederick II, who made him court reader and had him admitted to the Royal Academy of Sciences; Discours sur le bonheur followed, an attack on Stoic and Christian ethics
• 1751, died in Berlin on 11 November, in the house of the French envoy; the traditional account blames a feast at which he ate a large quantity of pheasant pâté with truffles. Frederick wrote his eulogy

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The core argument

La Mettrie's case is empirical, and it is stronger than its reputation.

1. The mind tracks the body. Fever, sleep, hunger, drugs, age and disease all change thought, mood and character. He collected clinical cases to show that "the faculties of the soul depend to such a degree on the proper organization of the brain and of the whole body, that apparently they are but this organization itself" (Man a Machine, Bussey translation).
2. Comparative anatomy. The differences between humans and other animals are differences of degree and organization, not of kind. He speculated that an ape might be taught to speak.
3. The soul is an empty word. If organization explains everything, the soul is "but an empty word, of which no one has any idea," and he concluded: "Let us then conclude boldly that man is a machine, and that in the whole universe there is but a single substance differently modified."
4. God is unproved and practically irrelevant. Here La Mettrie is more cautious than his reputation. He wrote: "I do not mean to call in question the existence of a supreme being; on the contrary it seems to me that the greatest degree of probability is in favor of this belief." But he added that this is "a theoretic truth with very little practical value," and that "it does not matter for our peace of mind, whether matter be eternal or have been created, whether there be or be not a God." He then reported, through the mouth of an unnamed friend, the view that "the universe will never be happy, unless it is atheistic."

The result is practical atheism: a world explained without God, with God left as an idle hypothesis. That is why later writers counted him among the atheists even though the text hedges.

A Christian response

Grant the data in full. The dependence of thought on the brain is real, and Christians have no stake in denying it. Scripture describes the human being as dust into which God breathed life: "Jehovah God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul" (Genesis 2:7, ASV). The question is not whether the mind depends on the body but whether it is nothing more than the body's mechanism.

The argument from reason. If every thought is fully explained by the motions of a machine, then La Mettrie's conclusion that man is a machine is itself only the output of those motions. Causes are not reasons. A machine that produces the sentence "man is a machine" has not thereby grasped that it is true. This is the point C. S. Lewis pressed and Alvin Plantinga refined: a thoroughgoing materialism cannot account for the reliability of the reasoning by which materialism is reached. See Argument from Reason, Argument from the Reliability of Reason and Self-refutation.

His own publisher said it first. Elie Luzac answered the book with L'Homme plus que machine. One of his objections, quoted in the notes to the Bussey edition, is the argument from reason in early form: if thought depended only on organization, how could the imagination "draw a long chain of consequences from the objects it has embraced?" Luzac also noted that the faculties growing and weakening with the body proves only that they depend on it, just as a musician depends on his instrument without being identical to it.

Consciousness and meaning. A machine description in third-person terms leaves out what it is like to be the person thinking, the problem Thomas Nagel later made famous. See Argument from Consciousness and Mind, Soul, Consciousness.

The happiness claim. La Mettrie put the claim that only atheism would make the world happy in a friend's mouth, and plainly found it attractive. The twentieth century's experiments in state atheism are relevant evidence on that point, as is the testimony of later atheists who found the godless universe anything but consoling. See Argument from Purpose Meaning and Hope.

See also

• Materialism, the metaphysics he championed
• Naturalism, the wider worldview
• Argument from Reason, the main Christian answer to his position
• Argument from the Reliability of Reason, Plantinga's development of it
• Argument from Consciousness, the case from subjective experience
• Mind, Soul, Consciousness, the domain hub
• Free Will and Determinism, since machine-man leaves no room for free choice
• Rene Descartes, whose animal-machine thesis La Mettrie extended to humans
• Atheism, the domain hub; La Mettrie stands in its Enlightenment section
• Jean Meslier, the earlier French materialist
• Thomas Nagel, a modern atheist who concedes materialism cannot explain mind