entering at length into the history of their
lives, but indicating the principal theories which they maintained, and
the main points in which they agreed with, or differed from, each other.

The earliest of them was _Thales_, who was born at Miletus, about 640 B.C.
He was a man of great political sagacity and influence; but we have to
consider him here as the earliest philosopher who appears to have been
convinced of the necessity of scientific proof of whatever was put forward
to be believed, and as the originator of mathematics and geometry. He was
also a great astronomer; for we read in Herodotus (i. 74) that he
predicted the eclipse of the sun which happened in the reign of Alyattes,
king of Lydia, B.C. 609. He asserted that water is the origin of all
things; that everything is produced out of it, and everything is resolved
into it. He also asserted that it is the soul which originates all motion,
so much so, that he attributes a soul to the magnet. Aristotle also
represents him as saying that everything is full of Gods. He does not
appear to have left any written treatises behind him: we are uncertain
when or where he died, but he is said to have lived to a great age--to 78,
or, according to some writers, to 90 years of age.

_Anaximander_, a countryman of Thales, was also born at Miletus, about 30
years later; he is said to have been a pupil of the former, and deserves
especial mention as the oldest philosophical writer among the Greeks. He
did not devote himself to the mathematical studies of Thales, but rather
to speculations concerning the generation and origin of the world; as to
which his opinions are involved in some obscurity. He appears, however, to
have considered that all things were formed of a sort of matter, which he
called {~GREEK SMALL LETTER TAU~}{~GREEK SMALL LETTER OMICRON WITH VARIA~} {~GREEK SMALL LETTER ALPHA WITH PSILI AND OXIA~}{~GREEK SMALL LETTER PI~}{~GREEK SMALL LETTER EPSILON~}{~GREEK SMALL LETTER IOTA~}{~GREEK SMALL LETTER RHO~}{~GREEK SMALL LETTER OMICRON~}{~GREEK SMALL LETTER NU~}, or The Infinite; which was something everlasting and
divine, though not invested with any spiritual or intelligent nature. His
own works have not come down to us; but, according to Aristotle, he
considered this "Infinite" as consisting of a mixture of simple,
unchangeable elements, from which all things were produced by the
concurrence of homogeneous particles already existing in it,--a process
which he attri