As to his philosophy, he is universally recognized as the first natural philosopher, but all one knows of him is little, and yet we seem to know the most of what there is. For since we find that the further philosophic progress of which his speculative idea was capable, and the understanding of his propositions, which they alone could have, make their first appearance and form particular epochs with the philosophers succeeding him, who may be recognized thereby, this development ascribed to Thales never took place with him at all. Thus if it is the case that a number of his other reflections have been lost, they cannot have had any particular speculative value; and his philosophy does not show itself to be an imperfect system from want of information about it, but because the first philosophy cannot be a system. We must listen to Aristotle as regards these ancient philosophers, for he speaks most sympathetically of them. In the passage of most importance (Metaph. I. 3), he says: “Since it is clear that we must acquire the science of first causes (_ἐξ ἀρχῆς αἰτίν_), seeing that we say that a person knows a thing when he becomes acquainted with its cause, there are, we must recollect, four causes—Being and Form first (for the ‘why’ is finally led back to the Notion, but yet the first ‘why’ is a cause and principle); matter and substratum, second; the cause whence comes the beginning of movement, third; and fourth the cause which is opposed to this, the aim in view and the good (for that is the end of every origination). Hence we would make mention of those who have undertaken the investigation of Being before us, and have speculated regarding the Truth, for they openly advance certain principles and first causes. If we take them under our consideration, it will be of this advantage, so far as our present investigation goes, that we shall either find other kinds of causes or be enabled to have so much the more confidence in those just named. Most of the earliest philosophers have placed the principles of everything in something in the form of matter (_ἐν ὕλης εἴδει_), for, that from which everything existent comes, and out of which it takes its origin as its first source, and into which it finally sinks, as substance (_οὐσία_), ever remains the same and only changes in its particular qualities (_πάθεσι_); and this is called the element (_στοιχεῖον_) and this the principle of all that exists” (the absolute prius). “On this account they maintain that nothing arises or passes away, because the same nature always remains. For instance, we say that, absolutely speaking, Socrates neither originates if he becomes beautiful or musical, nor does he pass away if he loses these qualities, because the subject (_τὸ ὑποκείμενον_), Socrates, remains the same. And so it is with all else. For there must be one nature, or more than one, from which all else arises, because it maintains its existence” (_σωζομένης ἐκείνης_),