The materialistic theory was in some sense sanctioned by those earlier Greek philosophers who referred the or- igin of all things — the spirit of man included — to some attenuated form of matter, as water, air, or fire. From these rude speculations philosophy emerged by succes- sive efforts, till in the Socratic school the soul of man was held to be distinct in its essence from matter, to be superior to matter, and indestructible by the dissolution of the body. The Socratic school also emphasized the doctrine that mind has infused order into the universe. The Platonic philosophy enforced these doctrines with glowing appeals to the nobler sentiments, and embel- lished them with a great variety of mythological repre- sentations. Aristotle, more cautious and exact in his statements, asserted for the higher forms of intellectual activity an essence distinct from matter. The philoso- jihers of the Epicurean school were avowed materialists. They taught explicitly and earnestly the doctrine that what is called the soul is composed of atoms, and must necessarily be dissipated at death. The universe itself likewise consists of atoms, and all its phenomena are the results of fortuitous combinations of atoms. Sensa- tion, intelligence, and desire are the effects of the action and reaction of the atoms within and the atoms with- out the body. These doctrines are elaborately set forth by the celebrated Lucretius (B.C. 95-44) in his poem De rerwn natura. The Atomic Materialism of Epicurus,
and the Imaginative and Rational Spiritualism of Plato and Aristotle, separated the Greek philosophers into two leading divisions, with various unimportant subordinate sections. Among the Jews, the Sadducees denied that there was either angel or spirit, or existence after death ; but there is no evidence that they supported these doctrines by any philosophical materialistic theo- ries. The Christian philosophy was necessarily anti- materialistic. With the revival of learning and of the ancient philosophies, the Epicurean materialism found many adherents, against whose influence the pronounced spiritualism of Descartes furnished a positive and most efiicient check. Hobbes was the opponent of Descartes, and all his conceptions of the soid and of the laws of its activity are materialistic, reducing all spiritual phenom- ena to bodily motions. Spinoza made spiritual beings to be modes of the universal substance which is God — every spiritual operation being the necessary counter- part of some materiahstic phenomenon. But the rise of the mechanical or new philosophj' of nature, to which Descartes incidentally contributed, and which Sir Isaac Newton so triumphantly established, had no little influ- ence in developing the materialism of modern philoso- phy. The speculations of Locke indirectly furthered this tendency ; although, with Descartes, he asserted the authority of consciousness for the realitj' of spiritual phenomena. But still he contended, as against Descar- tes, that no man has the right to aflirm that God could not endow matter with the capacity to think. The free-thmking Deists of England, who called themselves the disciples of Locke, were in many cases materialists, and advanced their speculations against the possibility of a separate existence of the soul in connection with their attacks upon the Christian doctrine of the resur- rection. There were few advocates of philosophical materialism among the English writers of the 18th cen- tury. David Hartley (1704-1757) made many phenom- ena of the soul to depend on vibrations of the brain, but expressly denied the inference that the soul is mate- rial in its substance. Joseph Priestley (1733-1804) was. led, in the course of his speculations, to assert that the soul is nothing but the organized body, and that this doctrine is essential to the rational acceptance of the Christian sj^stem (Disquisitions relatiiif/ to Matter and Spirit, London, 1777, 2 vols. 8vo). In France the influ- ence of the spiritualistic doctrines of Descartes was grad- ually displaced in the schools by the system of Condil- lac, which found its logical termination in the extreme materialism of La Mettrie (1709-1751), U Homme ma- chine ; Histoire naturelle de Vdme, and of baron Holbach (1723-1789), Systeme de la Nature, in which all spirit- ual essence and activity are resolved into matter and motion. Here the Encyclopjedists Diderot (q. v.) and D'Alembert (q. v.) deserve special mention ; nor should the noted Helvetius (q. v.) be forgotten.
In more recent times, materialism has been both metaphysical and physiological. IMetaphj'sical mate- rialism has resulted in some cases by logical deduc- tion, or, rather, a logical tendency, from the idealistic assumption that matter and spirit are identical. The argument which seeks to make matter and spirit one, lends plausibilitj' to the conclusion that it is indifferent whether matter should be resolved into spirit, or spirit resolved into matter. The extreme idealism of some of the German schools has prepared the way for the mate- rialism with which they would seem to have had the least possible sympathy. The real pantheism of Spinoza and the logical pantheism of Hegel have fiu-nished ax- ioms and a method, which have been applied in the serv- ice of materialism. It is in physiology, however, that modern materialism has found its most efiicient alh'. Physiology has renewed the previously-exploded doc- trine of vibrations, which again has found conlimiation in that view of the correlation of forces which resolves every agency of nature into some mode of motion. If heat, and light, and electricity are but modes of motion, why not nervous activity ? and if nervous activity, why