The great influence which has been exercised on civilized nations by the Christian beliefs, supported by the practical exigencies of the state, for thousands of years, was chiefly seen in the crude superstition of the mass of the people. Confessions of faith became as much a matter of routine as the latest fashion in dress or the latest custom, etc. But even the majority of the philosophers were more or less subordinated to the influence. It is true that a few great thinkers freed themselves by the use of pure reason at an early date from the prevalent superstition, and framed systems apart from tradition and the priests. But most philosophers could not rise to the altitude of these brave Free-thinkers; they remained "school-men" in the literal sense, dependent on the dictation of authority, the traditions of the school, and the dogmas of the Church. Philosophy was the "handmaid" of theology and ecclesiasticism. If we examine the history of philosophy in this light, we find in it a struggle for twenty-five hundred years between two great tendencies--the dualism of the majority (with theological and mystic leanings) and the monism of the minority (with rationalistic and naturalistic disposition). Especially notable are those great Free-thinkers of classic antiquity who taught a monistic view of life in the sixth century before Christ--the Ionic natural philosophers, Thales, Anaximander, and Anaximenes; and a little later, Heraclitus, Empedocles, and Democritus. They made the first thorough attempt to explain the world on rational principles, independently of all mythological tradition and theological dogmas. However, these remarkable efforts to found a primitive monism, which found so finished an expression in the _De rerum natura_ of the great poet-philosopher, Lucretius Carus (98-54 B.C.), were shortly thrust out by the spread--through Plato's curious dualism--of the belief in the immortality of the soul and the transcendental world of ideas.