David Hume was a Scottish philosopher, historian, economist, and essayist, best known for his highly influential system of empiricism, philosophical scepticism, and metaphysical naturalism. Beginning with A Treatise of Human Nature (1739–40), Hume strove to create a naturalistic science of man that examined the psychological basis of human nature.

Hume followed John Locke in rejecting the existence of innate ideas, concluding that all human knowledge derives solely from experience, placing him alongside figures like Francis Bacon, Thomas Hobbes, John Locke, and George Berkeley as an empiricist. He argued that inductive reasoning and belief in causality cannot be justified rationally; instead, they result from custom and mental habit. This problem of induction suggests that to draw any causal inferences from past experience, it is necessary to presuppose that the future will resemble the past, a metaphysical presupposition that cannot itself be grounded in prior experience.

An opponent of philosophical rationalists, Hume famously proclaimed that "Reason is, and ought only to be the slave of the passions." He was a sentimentalist who believed that ethics are based on emotion or sentiment rather than abstract moral principle, and he is often credited by historians of European philosophy with first clearly expounding the is–ought problem, or the idea that a statement of fact alone can never give rise to a normative conclusion of what ought to be done.

Hume denied that humans have an actual conception of the self, positing that we experience only a bundle of sensations, and that the self is nothing more than this bundle of perceptions connected by an association of ideas. Hume's compatibilist theory of free will takes causal determinism as fully compatible with human freedom. His philosophy of religion, including his rejection of miracles and critique of the argument from design for God's existence, were especially controversial for their time.

Hume left a legacy that affected utilitarianism, logical positivism, the philosophy of science, early analytic philosophy, cognitive science, theology, and many other fields and thinkers. Immanuel Kant credited Hume as the inspiration that had awakened him from his "dogmatic slumbers."