The theories of human origins that were produced in later times tended to be the products of wider philosophical systems, rather than of science as such. Most of them relied heavily on by orthodox notion that animal life developed out of the earth. Protagoras was one of the most famous of the Sophists, the loosely defined group of teachers who came to prominence in late fifth century Athens as purveyors of a popularly demanded education in rhetoric, politics, conduct and life in general. The Stoic school of philosophy was founded by Zeno soon after the rival Epicurean establishment, and like Epicureanism it was still attracting adherents as late as the third century AD. There are many resemblances between the two systems, but on the basic question of the mainspring of human morality and human history they are sharply divided. The Stoic system is an utterly theistic one, according to which there are two ultimate principles of existence, God and matter.