Who posited that a person knows something that exists, for a person who does not exist is nothing?

The correct answer is b. Parmenides.

Parmenides argued that reality is unchanging and that change is an illusion. He asserted that for something to be thought of or known, it must exist; thus, a person who does not exist cannot be known or thought of. His philosophy emphasizes the idea of being versus non-being, suggesting that nothing can come from nothing. If you need more detailed explanations or assistance, feel free to check the extended services page!