"Principia Metaphysica" is a philosophical work by Gottfried Wilhelm Leibniz, published in 1714. It explores the fundamental principles of reality, focusing on concepts such as substance, identity, and causation. Leibniz aims to establish a systematic framework for understanding the nature of existence and the relationships between entities. In this work, Leibniz introduces the idea of monads, which are simple, indivisible units that make up the fabric of the universe. He argues that these monads are the true substances, each reflecting the entire universe from its own perspective. This concept significantly influenced later philosophical thought, particularly in the realm of metaphysics.