Revolutions do not favor pure science, but they stimulate applied science to meet the needs of a society fighting for its liberty. So Lavoisier, the chemist-financier, helped the American and French Revolutions by improving the quality and production of gunpowder; Berthollet and other chemists, spurred by the English blockade, found substitutes for imported sugar, soda, and indigo. Lavoisier was guillotined as a profiteer (1794),54 but, a year later, the Revolutionary government repudiated this act, and honored his memory. The Convention protected the scientists on its committees, and accepted their plans for a metric system; the Directory gave scientists high status in the new Institut de France; Lagrange, Laplace, Adrien-Marie Legendre, Delambre, Berthollet, Lamarck, Cuvier—names still shining in the history of science—were among its earliest members. Science for a time replaced religion as the staple of French education; the return of the Bourbons interrupted this movement, but their fall (1830) was accompanied by the exaltation of science in the “positive philosophy” of Auguste Comte.

Lagrange and Legendre left their lasting marks on mathematics. Lagrange formulated the “calculus of variations,” whose equations are still part of the science of mechanics. Legendre worked on elliptic integrals from 1786 to 1827, when he published his results in a Traité des fonctions. Gaspard Monge, son of a peddler, invented descriptive geometry—a method of representing three-dimensional objects on a two-dimensional plane; he organized the national reclamation of copper and tin, wrote a famous text on the gentle art of manufacturing cannon, and served the Revolutionary government and Napoleon through a long career as mathematician and administrator. Laplace aroused the intelligentsia of Europe with his Exposition du système du monde (1796), which formulated a nebular hypothesis and tried to explain the universe as pure mechanism; when Napoleon asked him “Who made all this” machinery, Laplace replied, “I had no need of that hypothesis.” Lavoisier, founder of modern chemistry, served as chairman of the commission that formulated the metric system (1790). Berthollet advanced both theoretical and practical chemistry, helped Lavoisier establish a new chemical nomenclature, and helped his embattled country by his method of converting ore into iron and iron into steel. Xavier Bichat pioneered in histology by his microscopic studies of tissues. In 1797 he began a famous series of lectures on physiology and surgery; he summarized his findings in Anatomie générale (1801). In 1799, aged twenty-eight, he was appointed physician at the Hôtel-Dieu. He was embarking upon a study of organic changes produced by disease when a fall put an end to his life (1802) at the age of thirty-one.

Pierre Cabanis may serve as a transition to philosophy, for though his time knew him chiefly as a physician, posterity came to think of him as a philosopher. In 1791 he attended the last illness of the dying Mirabeau. He lectured at the École de Médecine on hygiene, legal medicine, and the history of medicine; for a time he was head of all the hospitals of Paris. He was one of the many distinguished men who discreetly loved the ever lovable widow of the philosophe Helvétius. At her gatherings he met Diderot, d’Alembert, d’Holbach, Condorcet, Condillac, Franklin, and Jefferson. As a student of medicine he was especially attracted to Condillac, who was then dominating the French philosophical scene with his doctrine that all knowledge comes from sensations. The materialistic implications of this sensationism appealed to Cabanis; they accorded well with the correlations that he had found between mental and bodily operations. He shocked even the advanced thinkers of his time by saying: “To form a correct idea of the operations whose result is thought, it is necessary to regard the brain as a special organ whose particular function is to produce thought, just as the stomach and the intestines have the special function of carrying on the work of digestion, the liver that of filtering the bile, etc.”55

Nevertheless Cabanis modified Condillac’s analysis by maintaining (as Kant had recently done in his Critique of Pure Reason) that a sensation enters an organism which is already half formed at birth, is molded thereafter by every experience, and carries its past in its cells and memories to form part of a changing personality, including internal sensations, reflexes, instincts, feelings, and desires. The psychophysical totality so produced molds to its structure and purpose every sensation that it receives. In this sense Cabanis agreed with Kant that the mind is not a helpless tabula rasa upon which sensations are impressed; it is an organization for transforming sensations into perceptions, thoughts, and actions. However (Cabanis insisted), the mind that Kant so revered is not an entity separable from the physiological apparatus of tissues and nerves.

This apparently materialistic system was expounded in the first (1796) of twelve mémoires which Cabanis published together in 1802 as Rapports du physique et du moral de l’homme. They reveal a powerful mind (or brain) eagerly active over a widening area of curiosity and speculation. The first essay is almost a survey of physiological psychology, studying the neural correlates of mental states. The third analyzes the “unconscious”: our accumulated memories (or neural inscriptions) may combine with external and internal sensations to generate dreams, or may unconsciously affect our ideas even in the most alert of waking states. The fourth holds that the mind ages with the body, so that the same person’s ideas and character may be quite different in his seventies than in his twenties. The fifth is a suggestive discussion of how glandular secretions—especially the sexual—may affect our feelings and thoughts. The tenth essay contends that man has evolved through chance variations or mutations which became hereditary.

In a book purporting to be Cabanis’ Lettres sur les causes premières (1824), published sixteen years after his death, he appears to retract his materialism, and to admit a First Cause endowed with intelligence and will.56 The materialist may remind us that the great surgeon had warned us against the effect of an aging body upon its associated mind. The skeptic may suppose that the mystery of consciousness had led Cabanis to suspect materialism of simplifying a very complex and immediate reality. In any event it is good that a philosopher should remind himself, now and then, that he is a particle pontificating on infinity.

Two men survived from the age of the philosophes to meet in person the Revolution that had been so fervently desired. When the Abbé Raynal, who had made his name in 1770 with Histoire philosophique … des deux Indes, saw the lumières of the Enlightenment darkened by the excesses of the populace, he sent to the Constituent Assembly, on May 31, 1791, a letter of protest and prophecy. “I have long dared to tell kings of their duties; let me today tell the people of their errors.” He warned that the tyranny of the crowd could be as cruel and unjust as the despotism of monarchs. He defended the right of the clergy to preach religion, so long as the opponents of religion or priestcraft were left free to speak their minds. He condemned alike the governmental financing of any religion (the state was then paying the salaries of priests) and the attacks upon priests by anticlerical mobs. Robespierre persuaded the irate Assembly to let the seventy-eight-year-old philosopher escape arrest, but Raynal’s property was confiscated, and he died in destitution and disillusionment (1796).

Constantin Chasseboeuf de Volney lived through the Revolution, and knew every notable in Paris from d’Holbach to Napoleon. After years of travel in Egypt and Syria he was elected to the States-General, and he served in the Constituent Assembly till its dissolution in 1791. In that year he published the philosophical echoes of his wanderings in Les Ruines, ou Méditations sur les révolutions des empires. What had caused the collapse of so many ancient civilizations? Volney answered that they had declined because of the ignorance induced in their people by supernatural religions allied with despotic governments, and by difficulties in the transmission of knowledge from generation to generation. Now that mythological creeds were losing their hold, and printing had facilitated the preservation of knowledge and the transference of civilization, men might hope to build lasting cultures upon a moral code in which knowledge, growing and spreading, would extend man’s control over his unsocial tendencies, and promote cooperation and unity. He was arrested in 1793 as a Girondin, and remained in prison for nine months. Released, he sailed to America, was welcomed by George Washington, was denounced as a French spy by President Adams (1798), and hurried back to France. He served as a senator under Napoleon, opposed the change from Consulate to Empire, and retired to a scholarly seclusion until Louis XVIII made him a peer in 1814. He died in 1820, having shared in deposing and restoring the Bourbons.

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