Metaphysics is a foundational branch of philosophy, described by figures like Aristotle as "first philosophy," that profoundly examines the fundamental structure of reality itself. It delves into a wide array of abstract concepts, including the nature of existence, the distinction between unique particulars and shared universals, and the complexities of space, time, causality, and free will.
Its historical roots are ancient and global, appearing in India's Upanishads, China's Daoism, and pre-Socratic Greece. Over centuries, it evolved through medieval debates on universals and modern philosophical systems embracing idealism, before facing 20th-century criticisms that spurred new approaches. While traditionally relying on rational intuition, it has recently incorporated empirical methods. Despite critiques regarding its abstract nature and methods, metaphysics remains crucial, implicitly informing many other fields of inquiry.