It acquires its first importance in the theories of Heraclitus (6th century B.C.), who, trying to account for the aesthetic order of the visible universe, broke away to some extent from the purely physical conceptions of his predecessors and discerned at work in the cosmic process a [Greek: logos] analogous to the reasoning power in man. On the one hand the Logos is identified with [Greek: gnômê] and connected with [Greek: dikê], which latter seems to have the function of correcting deviations from the eternal law that rules in things. On the other hand it is not positively distinguished either from the ethereal fire, or from the [Greek: heimarmenê] and the [Greek: anankê] according to which all things occur. Heraclitus holds that nothing material can be thought of without this Logos, but he does not conceive the Logos itself to be immaterial. Whether it is regarded as in any sense possessed of intelligence and consciousness is a question variously answered. But there is most to say for the negative. This Logos is not one above the world or prior to it, but in the world and inseparable from it. Man's soul is a part of it. It is _relation_, therefore, as Schleiermacher expresses it, or reason, not speech or word. And it is objective, not subjective, reason. Like a law of nature, objective in the world, it gives order and regularity to the movement of things, and makes the system rational.[1] The failure of Heraclitus to free himself entirely from the physical hypotheses of earlier times prevented his speculation from influencing his successors. With Anaxagoras a conception entered which gradually triumphed over that of Heraclitus, namely, the conception of a supreme, intellectual principle, not identified with the world but independent of it. This, however, was [Greek: nous], not Logos. In the Platonic and Aristotelian systems, too, the theory of ideas involved an absolute separation between the material world and the world of higher reality, and though the term Logos is found the conception is vague and undeveloped. With Plato the term selected for the expression of the principle to which the order visible in the universe is due is [Greek: nous] or [Greek: sophia], not [Greek: logos]. It is in the pseudo-Platonic _Epinomis_ that [Greek: logos] appears as a synonym for [Greek: nous]. In Aristotle, again, the principle which sets all nature under the rule of thought, and directs it towards a rational end, is [Greek: nous], or the divine spirit itself; while [Greek: logos] is a term with many senses, used as more or less identical with a number of phrases, [Greek: ou heneka], [Greek: energeia], [Greek: entelecheia], [Greek: ousia], [Greek: eidos], [Greek: morphê], &c.