Materialism argues that physical matter is the only reality and everything, including thoughts and feelings, can be explained by physical phenomena and matter. The document outlines three positive arguments for materialism: 1) Humans evolved from animals so we must be physical beings, 2) Advances in understanding the brain show mental conditions have physical causes, and 3) If advanced AI can behave like humans without minds, then humans may not have minds either. It also discusses two negative arguments against materialism around the interaction of minds and bodies and how we know other minds exist.