Laplace's demon is a thought experiment proposed by the French mathematician Pierre-Simon Laplace in the 18th century. It imagines a hypothetical intellect that knows the precise location and momentum of every particle in the universe at a given time. With this information, the demon could predict the future and understand the past, demonstrating a deterministic view of the universe. The concept raises questions about free will and determinism, suggesting that if everything is predictable, then human actions might also be predetermined. This idea has influenced discussions in philosophy, physics, and the nature of knowledge, highlighting the limits of human understanding in a complex universe.