David Hume (/hjuːm/; born David Home; 7 May 1711 NS (26 April 1711 OS) – 25 August 1776) was a Scottish philosopher, historian, economist, and essayist, who is best known today for his highly influential system of philosophical empiricism, skepticism, and naturalism. Hume's empiricist approach to philosophy places him with John Locke, Francis Bacon and Thomas Hobbes as a British Empiricist. Beginning with his A Treatise of Human Nature (1739), Hume strove to create a total naturalistic science of man that examined the psychological basis of human nature. Against philosophical rationalists, Hume held that passion rather than reason governs human behaviour. Hume argued against the existence of innate ideas, positing that all human knowledge is ultimately founded solely in experience; Hume thus held that genuine knowledge must either be directly traceable to objects perceived in experience, or result from abstract reasoning about relations between ideas which are derived from experience, calling the rest "nothing but sophistry and illusion", a dichotomy later given the name Hume's fork.

In what is sometimes referred to as Hume's problem of induction, he argued that inductive reasoning and belief in causality cannot ultimately be justified rationally; our trust in causality and induction instead results from custom and mental habit and are attributable to only the experience of "constant conjunction" rather than logic: for we can never, in experience, perceive that one event causes another, but only that the two are always conjoined, and to draw any inductive causal inferences from past experience first requires the presupposition that the future will be like the past, a presupposition which cannot be grounded in prior experience without already being presupposed. Hume's anti-teleological opposition to the argument for God's existence from design is generally regarded as the most intellectually significant such attempt to rebut the teleological argument prior to Charles Darwin.

Hume was also a sentimentalist who held that ethics are based on emotion or sentiment rather than abstract moral principle, famously proclaiming that "Reason is, and ought only to be the slave of the passions". Hume's moral theory has been seen as a unique attempt to synthesise the modern sentimentalist moral tradition to which Hume belonged, with the virtue ethics tradition of ancient philosophy, with which Hume concurred in regarding traits of character, rather than acts or their consequences, as ultimately the proper objects of moral evaluation. Hume maintained an early commitment to naturalistic explanations of moral phenomena, and is usually taken to have first clearly expounded 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 also 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 causally-connected perceptions. Hume's compatibilist theory of free will takes causal determinism as fully compatible with human freedom.

Hume influenced utilitarianism, logical positivism, Immanuel Kant, the philosophy of science, early analytic philosophy, cognitive science, theology, and other movements and thinkers. Kant himself credited Hume as the spur to his philosophical thought who had awakened him from his "dogmatic slumbers".