David Hume was a renowned Scottish philosopher, historian, economist, and essayist, best known for his influential system of empiricism, philosophical scepticism, and metaphysical naturalism. Beginning with A Treatise of Human Nature (1739–40), Hume aimed to create a naturalistic science of man, examining the psychological basis of human nature. He followed John Locke in rejecting the existence of innate ideas, concluding that all human knowledge derives solely from experience. This places him with other empiricists like Francis Bacon, Thomas Hobbes, John Locke, and George Berkeley.

Hume argued that inductive reasoning and belief in causality cannot be justified rationally; instead, they result from custom and mental habit. We never actually perceive that one event causes another but only experience the "constant conjunction" of events. This problem of induction means that to draw any causal inferences from past experience, it is necessary to presuppose that the future will resemble the past—this metaphysical presupposition cannot itself be grounded in prior experience.

An opponent of philosophical rationalists, Hume held that passions rather than reason govern human behaviour, famously proclaiming that "Reason is, and ought only to be the slave of the passions." Hume was also a sentimentalist who held that ethics are based on emotion or sentiment rather than abstract moral principle. He is usually accepted by historians of European philosophy as the first to clearly expound 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, was especially controversial for its 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."