Contemporary of Thales, this philosopher, born into a wealthy family, travelled in the Aegean islands, the Black Sea region, and in Egypt and Babylon where he studied mathematics and astronomy; built a solar clock, a heavenly sphere, and made a map of the earth.
He carried on the scientific work of his teacher, Thales, and wrote the work 'On Nature', believed to be the most ancient work written in prose, a work which has been lost.
We know of his works from the later, 4th to 3rd century BC philosopher , Theophrastus, who was an associated of an successor to Aristotle.
Anaximander believed that matter was infinite and uncorruptible, but he did not conceive of matter in the usual elemental terms commonly understood, but used the term to refer to a primordial substance from which all arose.
He also believed that the earth was formed by the condensation of liquid (echoing the thought of his teacher, Thales) through the action of the sun's heat, and that humans evolved from acquatic life forms, this latter belief representing perhaps the first theory of biological evolution (at least stated scientifically, since many concepts of the origins of life and of humankind have been expressed since earliest times in myths, folk tales and legends).
Anaximander's innovative ideas presaged many of the philosophical problems of the centuries that followed, up through modern times.