1. Thales.—At the head of the Ionic natural philosophers, and therefore at the head of philosophy, the ancients are generally agreed in placing Thales of Miletus, a cotemporary of Croesus and Solon; although this beginning lies more in the region of tradition than of history. The philosophical principle to which he owes his place in the history of philosophy is, that, “the principle (the primal, the original ground) of all things is water; from water every thing arises and into water every thing returns.” But simply to assume water as the original ground of things was not to advance beyond his myth-making predecessors and their cosmologies. Aristotle, himself, when speaking of Thales, refers to the old “theologians,”—meaning, doubtless, Homer and Hesiod,—who had ascribed to Oceanus and Thetis, the origin of all things. Thales, however, merits his place as the beginner of philosophy, because he made the first attempt to establish his physical principle, without resorting to a mythical representation, and, therefore, brought into philosophy a scientific procedure. He is the first who has placed his foot upon the ground of a logical (verstÄndig) explanation of nature. We cannot now say with certainty, how he came to adopt his principle, though he might have been led to it, by perceiving that dampness belonged to the seed and nourishment of things; that warmth is developed from moisture; and that, generally, moisture might be the plastic, living and life-giving principle. From the condensation and expansion of this first principle, he derives, as it seems, the changes of things, though the way in which this is done, he has not accurately determined.

The philosophical significance of Thales does not appear to extend any farther. He was not a speculative philosopher after a later mode. Philosophical book-making was not at all the order of his day, and he does not seem to have given any of his opinions a written form. On account of his ethico-political wisdom, he is numbered among the so-named “seven wise men,” and the characteristics which the ancients furnish concerning him only testify to his practical understanding. He is said e. g. to have first calculated an eclipse of the sun, to have superintended the turning of the course of the Halys under Croesus, &c. When subsequent narrators relate that he had asserted the unity of the world, had set up the idea of a world-soul, and had taught the immortality of the soul and the personality of God, it is doubtless an unhistorical reference of later ideas to a standpoint, which was, as yet, far from being developed.

2. Anaximander.—Anaximander, sometimes represented by the ancients as a scholar and sometimes as a companion of Thales, but who was, at all events, younger than the latter, sought to carry out still farther his principles. The original essence which he assumed, and which he is said to have been the first to have named principle (????), he defined as the “unlimited, eternal and unconditioned,” as that which embraced all things and ruled all things, and which, since it lay at the basis of all determinateness of the finite and the changeable, is itself infinite and undeterminate. How we are to regard this original essence of Anaximander is a matter of dispute. Evidently it was not one of the four common elements, though we must not, therefore, think it was something incorporeal and immaterial. Anaximander probably conceived it as the original matter before it had separated into determined elements,—as that which was first in the order of time, or what is in our day called the chemical indifference in the opposition of elements. In this respect his original essence is indeed “unlimited” and “undetermined,” i. e. has no determination of quality nor limit of quantity, yet it is not, therefore, in any way, a pure dynamical principle, as perhaps the “friendship” and “enmity” of Empedocles might have been, but it was only a more philosophical expression for the same thought, which the old cosmogonies have attempted to utter in their representation of chaos. Accordingly, Anaximander suffers the original opposition of cold and warm, of dry and moist (i. e. the basis of the four elements) to be secreted from his original essence, a clear proof that it was only the undeveloped, unanalyzed, potential being of these elemental opposites.

3. Anaximenes.—Anaximenes, who is called by some the scholar, and by others the companion of Anaximander, turned back more closely to the view of Thales, in that he made air as the principle of all things. The perception that air surrounds the whole world, and that breath conditions the activity of life, seems to have led him to his position.

4. Retrospect.—The whole philosophy of the three Ionic sages may be reduced to these three points, viz:—(1.) They sought for the universal essence of concrete being; (2.) They found this essence in a material substance or substratum; (3.) They gave some intimation respecting the derivation of the elements from this original matter.