and cows like cows". Another philosopher, Anaxagoras (5th century BCE), claimed that the Sun was "a fiery mass, larger than the Peloponnese"; a charge of impiety was brought against him, and he was forced to flee Athens. The first fully materialistic philosophy was produced by the atomists Leucippus and Democritus (5th century BCE), who attempted to explain the formation and development of the world in terms of the chance movements of atoms moving in infinite space. For political reasons, Socrates was accused of being atheos ("refusing to acknowledge the gods recognized by the state"). The Athenian public associated Socrates (c. 470–399 BCE) with the trends in pre-Socratic philosophy towards naturalistic inquiry and the rejection of divine explanations for phenomena. Aristophanes' comic play The Clouds (performed 423 BCE) portrayed Socrates as teaching his students that the traditional Greek deities did not exist. Socrates was later tried and executed under the charge of not believing in the gods of the state and instead worshipping foreign gods. Socrates himself vehemently denied the charges of atheism at his trial. in All the surviving sources about him indicate that he was a very devout man, who prayed to the rising sun and believed that the oracle at Delphi spoke the word of Apollo. While only a few of the ancient Greco-Roman schools of philosophy were subject to accusations of atheism, there were some individual philosophers who espoused atheist views. The Peripatetic philosopher Strato of Lampsacus did not believe in the existence of gods. The Cyrenaic philosopher Theodorus the Atheist (c. 300 BCE) is supposed to have denied that gods exist and wrote a book On the Gods expounding his views. The Sophists In the fifth century BCE the Sophists began to question many of the traditional assumptions of Greek culture. Prodicus of Ceos was said to have believed that "it was the things which were serviceable to human life that had been regarded as gods", and Protagoras stated at the beginning of a book that "With regard to the gods I am unable to say either that they exist or do not exist". Diagoras of Melos allegedly chopped up a wooden statue of Heracles and used it to roast his lentils and revealed the secrets of the Eleusinian Mysteries. The Athenians accused him of impiety and banished him from their city. Critias was said as well to deny that the gods existed. Epicureanism The most