The ante-Socratic schools were chiefly occupied with the study of external nature. "Greek philosophy was, at its first appearance, a philosophy of nature." It was an effort of the reason to reach a "first principle" which should explain the universe. This early attempt was purely speculative. It sought to interpret all phenomena by _hypotheses_, that is, by suppositions, more or less plausible, suggested by physical analogies or by _à priori_ rational conceptions. Now there are two distinct aspects under which nature presents itself to the observant mind. The first and most obvious is the _simple phenomena_ as perceived by the senses. The second is the _relations_ of _phenomena_, cognized by the reason alone. Let phenomena, which are indeed the first objects of perception, continue to be the chief and almost exclusive object of thought, and philosophy is on the highway of pure physics. On the other hand, instead of stopping at phenomena, let their relations become the sole object of thought, and philosophy is now on the road of purely mathematical or metaphysical abstraction. Thus two schools of philosophy are developed, the one SENSATIONAL, the other IDEALIST. Now these, it will be found, are the leading and characteristic tendencies of the two grand divisions of the pre-Socratic schools; the Ionian is _sensational_, the Italian is _idealist_. These two schools have again been the subject of a further subdivision based upon diverse habits of thought. The Ionian school sought to explain the universe by _physical analogies._ Of these there are two clear and obvious divisions--analogies suggested by living organisms, and analogies suggested by mechanical arrangements. One class of philosophers in the Ionian school laid hold on the first analogy. They regarded the world as a living being, spontaneously evolving itself--a vital organism whose successive developments and transformations constitute all visible phenomena. A second class laid hold on the analogy suggested by mechanical arrangements. For them the universe was a grand superstructure, built up from elemental particles, arranged and united by some ab-extra power or force, or else aggregated by some inherent mutual affinity. Thus we have two sects of the Ionian school; the first, _Dynamical_ or vital; the second, _Mechanical_.[400] [Footnote 400: Ritter's "Ancient Philosophy," vol. i. pp. 191, 192.]