In ancient india, it was the char walkers the materialist. Materialists say that mind is just products of chemical activity in your brain. That's what constitutes distinct personality. And bodyis just a very complicated form of matter. Somehow it produces the by product which you are. You're a by product. How do you know that? There's nothing else?
Swami Sarvapriyananda teaches the Katha Upanishad, which is one of the most popular Upanishads. The scripture concerns the story of a young man who goes to the house of death to find out what happens after death. The reply describes the nature of reality and the meaning of life.