Xenophanes (570 BC - 470 BC) was a Greek philosopher, poet, and social and religious critic. Our knowledge of his views comes from his surviving poetry, all of which are fragments passed down as quotations by later Greek writers. His poetry criticized and satirized a wide range of ideas, including the belief in the pantheon of anthropomorphic gods and the Greeks' veneration of athleticism.
Xenophanes rejected the then standard belief in many gods, as well as the idea that the gods resembled humans in form. One famous passage ridiculed the idea by claiming that, if oxen were able to imagine gods, then those gods would be in the image of oxen. Because of his development of the concept of One God that is abstract, universal, unchanging, immobile and always present, Xenophanes is often seen as one of the first monotheists in occidental philosophy of religion.
He also wrote that poets should only tell stories about the gods which were socially uplifting, one of many views which foreshadowed the work of Plato. Xenophanes also concluded from his examination of fossils that water once must have covered all of Earth's surface. His epistemology, which is still influential today, held that there actually exists a truth of reality, but that humans as mortals are unable to cognize it. Therefore, it is possible to act only on the basis of working hypotheses - we may act as if we knew the truth, as long as we know that this is extremely unlikely. This aspect of Xenophanes was brought out again by the late Sir Karl Popper and is a basis of Critical Rationalism.
Until the 1950s, there was some controversy over many aspects of Xenophanes, including whether or not he could be properly characterized as a philosopher. In today's philosophical and classics discourse, Xenophanes is seen as one of the most important presocratic philosophers. It had also been common to see him as the teacher of Zeno of Elea, the colleague of Parmenides, and generally associated with the Eleatic school, but common opinion today is likewise that this is false.
H. Diels and W. Kranz (eds.), Die Fragmente der Vorsokratiker, 6th edn. Zurich 1968 (standard work; much superior to Kirk/Raven)
B. Gentili and C. Prato (eds.), Poetarum Elegiacorum Testimonia et Fragmenta 1, Leipzig 1988 (best Greek text available)
J.H. Lesher (ed.), Xenophanes. Fragments, Toronto 1992 (best English edition and translation)