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 Crœsus, &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 (ἀρχὴ), 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.