If the period of the Middle Ages is excepted, when philosophical thought was determined mainly by theological conceptions, materialism may be said to have held a place throughout the whole history of philosophy. We have al ready noticed some of the forms in which this mode of thought continues to appear at the present day, and may now refer briefly to its more important historical representatives. The systems of the early Greek philosophers who found the fundamental principle of things in some physical substance, such as water, air or fire, cannot properly be classed as materialism. For as yet there was no opposition between the material and the spiritual. Neither the concep tion of matter as lifeless and unintelligent sub stance, nor of mind as an immaterial directing principle, had yet been formed. Atomism, as developed by Democritus of Abdera, is the first thoroughgoing system of materialism. Democritus taught that the soul, like everything else, is an aggregate composed of atoms. The soul-atoms differ from all the others in being the finest,, smoothest and most mobile. When they are in isolation, they are insensible, but from their union sensation arises. From sensa tion all the other processes of the mental life originate. The same conclusions were main tained by the Epicureans, who adopted with out any essential modification the theory of atomism. In spite of the statement of the Stoics that whatever exists is corporeal, their system cannot properly be described as materialism. For the human soul and God, the all-embracing Logos of which the human reason is a spark of emanation, though constantly de scribed in materialistic terms, yet function ideally as rational directing forces.
Materialism was revived in modern times by Gassendi (1592-1655) (q.v.) under the form of atomism. Modern materialism was, however, first worked out by Thomas Hobbes (q.v.), who based it upon the mechanical conceptions which in his day were being made the basis of all physical science. He did not deny the existence of immaterial things — God, angels, pure spirits — but shrewdly contented himself with showing that only that which is composed of parts, that is, bodies, can be the object of thought and so be known. All real phenomena
must therefore be explained in accordance with the mechanical theory and in terms of the move ment of bodies. Under the influence of the de veloping physical sciences and especially of the dominant conception of mechanism, material istic tendencies played an important part in the thought of the 18th century. David Hartley (1704-57) and Joseph Priestley (1733-1804) (q.v.) definitely subordinated the mental life to the bodily processes, though the latter at tempts to reconcile his materialism with Chris tianity and even to support it by appealing to the Bible. It is in France, however, in the systems of La Mettrie (1709-51), Baron d'Hol bach (1723-89), and Cabanis (1757-1808) (q.v.) that we find in this century representa tives of materialism who do not hesitate to draw the most extreme consequences of their doctrine, to deny the existence of God and to reduce man to a mere piece of physical mechanism. Again, in the middle of the 19th century, a revival of materialism occurred in Germany which had an important popular influence. The most important names connected with this movement are Carl Vogt, J. Moleschott, H. Czolbe and Louis Buchner (whose book, 'Kraft rind Stoff'—'Force and Matter'—has been called the Bible of German materialism, and has passed through numerous editions in its English translation). The general adoption of the evoltsionary point of view was in the beginning at least favorable to materialism. The philosophical problem seemed to be to derive from some primitive form of matter all the various modes of existence in accordance with the established laws of physical evolution. To this task Herbert Spencer (q.v.) devoted his life with a result that is variously estimated in different quarters. It can at least be said that at present thinkers are more inclined than formerly to question the adequacy of physical science to furnish a complete and final explana tion of the nature of the evolutionary process.
Bibliography.— Lange, 'Geschichte des Ma terialismusl (Eng. trans., 3 vols., London 1878 81) Buchner, 'Force and Matter' (London 1864) ; Haeckel, The Riddle of the Universe' (New York 1899) ; Paulsen, 'Introduction to Philosophy' (New York 1895).