The ancient Greek philosopher Thales was born in Miletus in Greek Ionia.Aristotle, the major source for Thales's philosophy and science, identified Thales as the first person to investigate the basic principles, the question of the originating substances of matter and, therefore, as the founder of the school of natural philosophy.Thales was interested in almost everything, investigating almost all areas of knowledge, philosophy, history, science, mathematics, engineering, geography, and politics.

Xenophanes, Herodotus, Heraclitus and Democritus were familiar with the work of Thales, and may have had a work by Thales available to them.

Proclus recorded that Thales was followed by a great wealth of geometers, most of whom remain as honoured names. Other philosophers who were credited with written works, who worked on topics similar to those of Thales, and who may have provided material for later writers, are Heraclitus of Ephesus, Anaxagoras of Clazomenae, Alcmaeon, Hippo of Samos, and Hippias of Elis.

They commence with Mamercus, who was a pupil of Thales, and include Hippias of Elis, Pythagoras, Anaxagoras, Eudoxus of Cnidus, Philippus of Mende, Euclid, and Eudemus, a friend of Aristotle, who wrote histories of arithmetic, of astronomy, and of geometry, and many lesser known names. 2), and the writing of Anaximenes was simple and unaffected (D. Aristotle defined wisdom as knowledge of certain principles and causes (, the originating principle.

Thales was much involved in the problems of astronomy and provided a number of explanations of cosmological events which traditionally involved supernatural entities.

His questioning approach to the understanding of heavenly phenomena was the beginning of Greek astronomy.

Thales' hypotheses were new and bold, and in freeing phenomena from godly intervention, he paved the way towards scientific endeavor.

He founded the Milesian school of natural philosophy, developed the scientific method, and initiated the first western enlightenment.

A number of anecdotes is closely connected to Thales' investigations of the cosmos. 475) specifically attributed to Thales authorship of the so-called Nautical Star-guide.

When considered in association with his hypotheses they take on added meaning and are most enlightening. Doubts have always existed about whether Thales wrote anything, but a number of ancient reports credit him with writings. Diogenes Laertius raised doubts about authenticity, but wrote that 'according to others [Thales] wrote nothing but two treatises, one 18. Hesychius, recorded that '[Thales] wrote on celestial matters in epic verse, on the equinox, and much else' (DK, 11A2). Diogenes mentions a poet, Choerilus, who declared that '[Thales] was the first to maintain the immortality of the soul' (D. I.24), and in Aristotle's words 'from what is recorded about [Thales]', indicate that Aristotle was working from a written source.

Thales was highly esteemed in ancient times, and a letter cited by Diogenes Laertius, and purporting to be from Anaximenes to Pythagoras, advised that all our discourse should begin with a reference to Thales (D. Callimachus credited Thales with the sage advice that navigators should navigate by Ursa Minor (D. Diogenes recorded that '[Thales] seems by some accounts to have been the first to study astronomy, the first to predict eclipses of the sun and to fix the solstices; so Eudemus in his History of Astronomy. Eudemus who wrote a History of Astronomy, and also on geometry and theology, must be considered as a possible source for the hypotheses of Thales.

It was this which gained for him the admiration of Xenophanes and Herodotus and the notice of Heraclitus and Democritus' (D. The information provided by Diogenes is the sort of material which he would have included in his History of Astronomy, and it is possible that the titles On the Solstice, and On the Equinox were available to Eudemus.