A Treatise of Human Nature

David Hume’s A Treatise of Human Nature, published anonymously in 1739–40, is a foundational work of empiricist philosophy. Hume sought to apply Newtonian experimental method to the human mind, proposing a “science of man” grounded in observation of mental life. The Treatise is divided into three books: Of the Understanding, Of the Passions, and Of Morals. In Book One, Hume argues that all ideas derive from impressions—sensory experiences and feelings—and that complex ideas are built by association through resemblance, contiguity, and causation. His analysis of causation is especially distinctive: we never perceive a necessary connection between cause and effect, only constant conjunction and a customary transition of the mind. Belief in causation is thus a product of habit, not reason. He also denies the existence of a stable, simple self, describing the mind as a bundle of perceptions. Book Two examines the passions, arguing that reason is and ought only to be the slave of the passions, and that sympathy transmits emotions between people. Book Three develops a moral theory in which moral judgments arise from sentiment rather than reason, with the “calm passions” and the general point of view shaping our approvals and disapprovals. The Treatise initially attracted little attention, but Hume’s later Enquiries reworked its central arguments. Its skepticism about induction, personal identity, and rationalist ethics remains widely debated in epistemology, metaphysics, and moral philosophy.