This paper explores Plato and Aristotle 's responses to the pre-Socratic philosopher Parmenides, who paradoxically said that there is no such thing as non-being, and no such things as change. I argue that Plato’s response would have been good enough to defeat the claim in a debate, thereby remedying the political aspects of the Parmenides problem. However, Aristotle ’s answer is required to answer some additional philosophical and scientific aspects. Plato's Sophist is a very difficult dialogue to understand; seeing it (...) in light of Aristotle 's discussion of the same topic helps to explain the complexities of what his teacher Plato wrote. (shrink)