Most of the earliest philosophers conceived only of material principles as underlying all things. That of which all things consist, from which they first come and into which on their destruction they are ultimately resolved, of which the essence persists although modified by its affections—this, they say, is an element and principle of existing things. Hence they believe that nothing is either generated or destroyed, since this kind of primary entity always persists. Similarly we do not say that Socrates comes into being absolutely when he becomes handsome or cultured, nor that he is destroyed when he loses these qualities; because the substrate, Socrates himself, persists. In the same way nothing else is generated or destroyed; for there is some one entity (or more than one) which always persists and from which all other things are generated. All are not agreed, however, as to the number and character of these principles. Thales, Thales of Miletus , fl. 585 B.C. the founder of this school of philosophy, That of the Ionian monists, who sought a single material principle of everything. says the permanent entity is water (which is why he also propounded that the earth floats on water). Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption, then, from this; and also from the fact that the seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things. There are some Cf. Plat. Crat. 402b , Plat. Theaet. 152e , Plat. Theaet. 180c,d . who think that the men of very ancient times, long before the present era, who first speculated about the gods, also held this same opinion about the primary entity. For they cf. Hom. Il. 14. 201 , Hom. Il. 14.246 . represented Oceanus and Tethys to be the parents of creation, and the oath of the gods to be by water— Styx, Cf. Hom. Il. 2.755 , Hom. Il. 14.271 , Hom. Il.15.37 . as they call it. Now what is most ancient is most revered, and what is most revered is what we swear by. Whether this view of the primary entity is really ancient and time-honored may perhaps be considered uncertain; however, it is said that this was Thales’ opinion concerning the first cause. (I say nothing of Hippo, Hippo of Samos , a medical writer and eclectic philosopher who lived in the latter half of the fifth century B.C. Cf. Aristot. De Anima 405b 2 . because no one would presume to include him in this company, in view of the paltriness of his intelligence.)