%3. Skepticism and Materialism.%
The ideas thus far developed move in a direction whose further pursuit inevitably issues in materialism. Diderot, the editor of the Encyclopedia of the Sciences, Arts, and Trades (1751-72), which gathered all the currents of the Illumination into one great stream and carried them to the open sea of popular culture, reflects in his intellectual development the dialectical movement from deism through skepticism to atheism and materialism, and was a co-laborer in the work which brought the whole movement to a conclusion, Holbach's System of Nature. Two decades, however, before the latter work, the outcome of a long development of thought, appeared, the physician La Mettrie[1] (1709-51) had promulgated materialism, though rather in an anthropological form than as a world-system, and with cynical satisfaction in the violation of traditional beliefs—in his Natural History of the Soul, 1745, in a disguised form, and, undisguised, in his Man a Machine, 1748—and at the same time (Anti-Seneca, or Discourse on Happiness, 1748) had sketched out for Helvetius the outlines of the sensationalistic morality of interest. While ill with a violent fever he observed the influence of the heightened circulation of the blood on his mental tone, and inferred that thought is the result of the bodily organization. The soul can only be known from the body. The senses, the best philosophers, teach us that matter is never without form and motion; and whether all matter is sentient or not, certainly all that is sentient is material, and every part of the organism contains a vital principle (the heart of a frog beats for an hour after its removal from the body; the parts of cut-up polyps grow into perfect animals). All ideas come from without, from the senses; without sense-impressions no ideas, without education, few ideas, the mind of a man grown up in isolation remains entirely undeveloped; and since the soul is entirely dependent on the bodily organs, along with which it originates, grows, and declines, it is subject to mortality. Not only animals, as Descartes has shown, but men, who differ from the brutes only in degree, are mere machines; by the soul we mean that part of the body which thinks, and the brain has fine muscles for thinking as the leg its coarse ones for walking.
[Footnote 1: La Mettrie was born at St. Malo, and educated in Paris, and in Leyden under Boerhave; he died in Berlin, whither Frederick the Great had called him after he had been driven out of his native land and from Holland. On La Mettrie cf. Lange, History of Materialism, vol. ii. pp. 49-91; and DuBois-Reymond's Address, 1875.]
If man is nothing but body, there is no other pleasure than that of the body. There is a difference, however, between sensuous pleasure, which is intense and brief, and intellectual pleasure, which is calm and lasting. The educated man will prefer the latter, and find in it a higher and more noble happiness; but nature has been just enough to grant the common multitude, in the coarser pleasures, a more easily attainable happiness. Enjoy the moment, till the farce of life is ended! Virtue exists only in society, which restrains from evil by its laws, and incites to good by rousing the love of honor. The good man, who subordinates his own welfare to that of society, acts under the same necessity as the evil-doer; hence repentance and pangs of conscience, which increase the amount of pain in the world, but are incapable of effecting amendment, are useless and reprehensible: the criminal is an ill man, and must not be more harshly punished than the safety of society requires. Materialism humanizes and exercises a tranquilizing influence on the mind, as the religious view of the world, with its incitement to hatred, disturbs it; materialism frees us from the sense of guilt and responsibility, and from the fear of future suffering. A state composed of atheists, is not only possible, as Bayle argued, but it would be the happiest of all states.
Among the editors of the Encyclopedia, the mathematician D'Alembert (Elements of Philosophy, 1758) remained loyal to skeptical views. Neither matter nor spirit is in its essence knowable; the world is probably quite different from our sensuous conception of it. As Diderot (1713-84), and the Encyclopedia with him, advanced from skepticism to materialism, D'Alembert retired from the editorial board (1757), after Rousseau, also, had separated himself from the Encyclopedists. Diderot[1] was the leading spirit in the second half of the eighteenth century, as Voltaire in the first half. His lively and many-sided receptivity, active industry, clever and combative eloquence, and enthusiastic disposition qualified him for this rôle beyond all his contemporaries, who testify that they owe even more to his stimulating conversation than to his writings. He commenced by bringing Shaftesbury's Inquiry into Virtue and Merit to the notice of his countrymen; and then turned his sword, on the one hand, against the atheists, to refute whom, he thought, a single glance into the microscope was sufficient, and, on the other, against the traditional belief in a God of anger and revenge, who takes pleasure in bathing in the tears of mankind. Then followed a period of skepticism, which is well illustrated by the prayer in the Thoughts on the Interpretation of Nature, 1754: O God! I do not know whether thou art, but I will guide my thoughts and actions as though thou didst see me think and act, etc. Under the influence of Holbach's circle he finally reached (in the Conversation between D'Alembert and Diderot, and D'Alembert's Dream, written in 1769, but not published until 1830, in vol. iv. of the Mémoires, Correspondance, et Ouvrages Inédits de Diderot) the position of naturalistic monism—there exists but one great individual, the All. Though he had formerly distinguished thinking substance from material substance, and had based the immortality of the soul on the unity of sensation and the unity of the ego, he now makes sensation a universal and essential property of matter (la pierre sent), declares the talk about the simplicity of the soul metaphysico-theological nonsense, calls the brain a self-playing instrument, ridicules self-esteem, shame, and repentance as the absurd folly of a being that imputes to itself merit or demerit for necessary actions, and recognizes no other immortality than that of posthumous fame. But even amid these extreme conclusions, his enthusiasm for virtue remains too intense to allow him to assent to the audacious theories of La Mettrie and Helvetius.
[Footnote 1: Works in twenty-two vols., Paris, Brière, 1821; latest edition, 1875 seq. Cf. on Diderot the fine work by Karl Rosenkranz, Diderots Leben und Werke, 1866.]
French natural science also tended toward materialism. Buffon (Natural History, 1749 seq) endeavors to facilitate the mechanical explanation of the phenomena of life by the assumption of living molecules, from which visible organisms are built up. Robinet (On Nature, 1761 seq.), availing himself of Spinozistic and Leibnitzian conceptions, goes still further, in that he endows every particle of matter with sensation, looks on the whole world as a succession of living beings with increasing mentality, and subjects the interaction of the material and psychical sides of the individual, as well as the relation of pleasure and pain in the universe, to a law of harmonious compensation.
The System of Nature, 1770, which bore on its title page the name of Mirabaud, who had died 1760, proceeded from the company of freethinkers accustomed to meet in the hospitable house of Baron von Holbach (died 1789), a native of the Palatinate. Its real author was Holbach himself, although his friends Diderot, Naigeon, Lagrange, the mathematician, and the clever Grimm (died 1807) seem to have co-operated in the preparation of certain sections. The cumbrous seriousness and the dry tone of this systematic combination of the radical ideas which the century had produced, were no doubt the chief causes of its unsympathetic reception by the public. Similarly unsuccessful was the popular account of materialism with which Holbach followed it, in 1772, and Helvetius's excerpts from the System of Nature, 1774.
Holbach applies himself to the despiritualization of nature and the destruction of religious prejudices with sincere faith in the sacred mission of unbelief—the happiness of humanity depends on atheism. "O Nature, sovereign of all beings, and ye her daughters, Virtue, Reason, and Truth, be forever our only divinities." What has made virtue so difficult and so rare? Religion, which divides men instead of uniting them. What has so long delayed the illumination of the reason, and the discovery of truth? Religion with its mischievous errors, God, spirit, freedom, immortality. Immortality exists only in the memory of later generations; man is the creature of a day; nothing is permanent but the great whole of nature and the eternal law of universal change. Can a clock broken into a thousand pieces continue to mark the hours? The senseless doctrine of freedom was invented only to solve the senseless problem of the justification of God in view of the existence of evil. Man is at every moment of his life a passive instrument in the hands of necessity; the universe is an immeasurable and uninterrupted chain of actions and reactions, an eternal round of interchanging motions, ruled by laws, a change in which would at once alter the nature of all things. The most fatal error is the idea of human and divine spirits, which has been advanced by philosophers and adopted with applause by fools. The opinion that man is divided into two substances is based on the fact that, of the changes in our body, we directly perceive only the external molar movements, while, on the other hand, the inner motions of the invisible molecules are known only by their effects. These latter have been ascribed to the mind, which, moreover, we have adorned with properties whose emptiness is manifested by the fact that they are all mere negations of that which we know. Experience reveals to us only the extended, the corporeal, the divisible—but the mind is to be the opposite of all three, yet at the same time to possess the power (how, no man can tell) of acting on that which is material and of being acted upon by it. In thus dividing himself into body and soul, man has in reality only distinguished between his brain and himself. Man is a purely physical being. All so-called spiritual phenomena are functions of the brain, special cases of the operation of the universal forces of nature. Thought and volition are sensation, sensation is motion. The moving forces in the moral world are the same as those in the physical world; in the latter they are called attraction and repulsion, in the former, love and hate; that which the moralist terms self-love is the same instinct of self-preservation which is familiar in physics as the force of inertia.
As man has doubled himself, so also he has doubled nature. Evil gave the first impulse to the formation of the idea of God, pain and ignorance have been the parents of superstition; our sufferings were ascribed to unknown powers, of which we were in fear, but which, at the same time, we hoped to propitiate by prayer and sacrifice. The wise turned with their worship and reverence toward a more worthy object, to the great All; and, in fact, if we seek to give the word God a tenable meaning, it signifies active nature. The error lay in the dualistic view, in the distinction between nature and itself, i.e. its activity, and in the belief that the explanation of motion required a separate immaterial Mover. This assumption is, in the first place, false, for since the All is the complex of all that exists there can be nothing outside it; motion follows from the existence of the universe as necessarily as its other properties; the world does not receive it from without, but imparts it to itself by its own power. In the second place the assumption is useless; it explains nothing, but confuses the problems of natural science to the point of insolubility. In the third place it is self-contradictory, for after theology has removed the Deity as far away from man as possible, by means of the negative metaphysical predicates, it finds itself necessitated to bring the two together again through the moral attributes—which are neither compatible with one another nor with the meta-physical—and crowns the absurdity by the assurance that we can please God by believing that which is incomprehensible. Finally, the assumption is dangerous; it draws men away from the present, disturbs their peace and enjoyment, stirs up hatred, and thus makes happiness and morality impossible. If, then, utility is the criterion of truth, theism—even in the mild form of deism—is proven erroneous by its disastrous consequences. All error is bane.