Anaximander

Anaximander of Miletus, pupil and associate of Thales, was among the boldest of the early thinkers. He held that the first principle is not any familiar substance but the apeiron — the boundless, indefinite source from which all things separate out and to which they return.

His single surviving sentence, preserved by Simplicius, speaks of things paying one another penalty for their injustice 'according to the ordinance of time' — the earliest fragment of Western philosophical prose. He is also credited with the first map of the world, a model of the heavens, and a theory that humankind descended from creatures of the sea.