What is the study of the fundamental nature of reality and existence called?

The study of the fundamental nature of reality and existence is known as metaphysics. This branch of philosophy explores questions related to what exists, the nature of objects and their properties, space and time, causality, and the relationship between mind and matter. Metaphysics delves into concepts that underlie our understanding of the world and our place within it, making it a foundational area of philosophical inquiry.

In contrast, epistemology focuses on the nature and scope of knowledge and belief, investigating how we know what we know. Logic deals with principles of valid reasoning and argumentation, while aesthetics concerns itself with the nature of beauty, art, and taste. Each of these branches of philosophy addresses different aspects of human experience and understanding, but only metaphysics centers directly on the fundamental nature of reality and existence.