founder of the school. Other eminent Eleatics include Zeno of Elea and Melissus of Samos. According to Aristotle and Diogenes Laertius, Xenophanes was Parmenides' teacher, and it is debated whether Xenophanes should also be considered an Eleatic. Parmenides was born in Elea to a wealthy family around 515 BCE. Parmenides of Elea was interested in many fields, such as biology and astronomy. He was the first to deduce that the earth is spherical. He was also involved in his town's political life. Parmenides' contributions were paramount not only to ancient philosophy but to all of western metaphysics and ontology. Parmenides wrote a hard to interpret poem, named On Nature or On What-is, that substantially influenced later Greek philosophy. Only 150 fragments of this poem survive. It tells a story of a young man (kouros in ancient Greek) dedicated to finding the truth carried by a goddess on a long journey to the heavens. The poem consists of three parts, the proem (i.e., preface), the Way of Truth and the Way of Opinion. Very few pieces from the Way of Opinion survive. In that part, Parmenides must have been dealing with cosmology, judging from other authors' references. The Way of Truth was then, and is still today, considered of much more importance. In the Way of Truth, the goddess criticizes the logic of people who do not distinguish the real from the non-existent ("What-is" and "What-is-Not"). In this poem Parmenides unfolds his philosophy: that all things are One, and therefore nothing can be changed or altered. Hence, all the things that we think to be true, even ourselves, are false representations. What-is, according to Parmenides, is a physical sphere that is unborn, unchanged, and infinite. This is a monist vision of the world, far more radical than that of Heraclitus. The goddess teaches Kouros to use his reasoning to understand whether various claims are true or false, discarding senses as fallacious. Other fundamental issues raised by Parmenides' poem are the doctrine that nothing comes from nothing and the unity of being and thinking. As quoted by DK fragment 3: To gar auto noein estin te kai einai (For to think and to be is one and the same). Zeno and Melissus continued Parmenides' thought on cosmology. Zeno is mostly known for his paradoxes, i.e., self-contradictory statements which served as proofs that Parmenides' monism was valid, and that pluralism was invalid. The