PHILOSOPHY: THE IONIAN SCHOOL.--The Greeks were the first to investigate rationally the causes of things, and to try to comprehend the world as a complete system. The earliest phase of this movement was on the side of physics, or natural philosophy. _Homer_ and _Hesiod_ had accounted for the operations of nature by referring them to the direct personal action of different divinities. The earliest philosophers brought in the conception of some kind of matter as the foundation and source of all things. The _Ionian School_ led the way in this direction. _Thales_ of Miletus (about 600 B.C.) made this primary substance to be _water_. _Anaximander_ (611-? B.C.) made all things spring out of a primitive stuff, without definite qualities, and without bounds. He taught that the earth is round, invented the sun-dial, engraved a map on a brass tablet, and made some astronomical calculations. _Anaximenes_ (first half, 6th C.) derived all things from _air_, which he made to be eternal and infinite. THE ELEATIC SCHOOL.--The _Eleatic School_ conceived of the world as one in substance, and held that the natural phenomena which we behold, in all their variety and change, are unreal. _Xenophanes_ (who flourished from 572 to 478 B.C.) asserted this. _Parmenides_ (504-460 B.C.) taught that succession, change, the manifold forms of things, are only _relative_; that is, are only our way of regarding the one universal essence. _Zeno_ sought to vindicate this theory logically by disproving the possibility of motion. OTHER PHILOSOPHERS.--Another set of philosophers attempted definitely to explain the appearances of things, the changing phenomena, which had been called unreal. _Heraclitus_ made the world to be nothing but these: There is no substratum of things: there is only an endless flux, a cycle. All things begin and end in fire, the symbol of what is real. _Empedocles_ ascribed all things to fire, air, earth, and water, which are wrought into different bodies by "love" and "hate;" or, as we should say, attraction and repulsion. _Democritus_ was the founder of the _Atomists_, who made all things spring out of the motions and combinations of primitive atoms. _Anaxagoras_ brought in intelligence, or reason, as giving the start to the development of matter,--this principle doing nothing more, however, and being inherent in matter itself. PYTHAGORAS.--A different spirit in philosophy belonged to _Pythagoras_ (580-500 B.C.), who was born in Samos, traveled extensively, and settled in Croton, in southern Italy. His theory was, that the inner substance of all things is number. Discipline of character was a prime object. Pythagoras was sparing in his diet, promoted an earnest culture, in which music was prominent, and gave rise to a mystical school, in which moral reform and religious fueling were connected with an ascetic method of living.