Thomas Reid (1710–96) was a contemporary of both Hume and Kant. He was born in Strachan, near Aberdeen, and was a founder and central figure in the Scottish school of common sense philosophy. Educated at Marishal College, Aberdeen, Reid served as Librarian there, and then as Minister at New Machar. While regent at King’s College, Reid cofounded the Aberdeen Philosophical Society, or Wise Club (1758), other members of which included George Campbell, Alexander Gerard, John Stewart and James Beattie. During this period, Reid published his first major work, An Inquiry into the Human Mind on the Principles of Common Sense (1764). That same year, he succeeded Adam Smith in the professorship of Moral Philosophy in Glasgow College, where he remained for the rest of his life. Reid published two other major works, Essays on the Intellectual Powers of Man (1785) and Essays on the Active Powers of Man (1788).
Reid himself claimed that his main achievement was having called into question the widely held view (‘the theory of ideas’) that the immediate object of thought is always some idea in the mind of the thinker, the sceptical tendencies of which Hume brought to full fruition. But his philosophy contains many important positive contributions beyond that, including an articulation of the first principles of common sense, which he took to be the foundation of all thought and action, philosophical or otherwise. In place of the theory of ideas, Reid defended direct theories of memory and perception. As part of his critique of Hume and his predecessors, Reid articulates a distinction between sensation and perception and provides an account of how experience extends our perceptual powers. Reid rejects a picture of the individual as cut off from the world, and as passively registering various images and feelings. Most of the mind’s operations incorporate judgment, according to Reid. And our judgments, though fallible, yield knowledge of such matters as our nature and wellbeing require, including knowledge of material things and their properties, past events, states of others’ minds, and moral and aesthetic facts.
Accompanying the movement away from the excessive, idea-centred individualism of previous theories is the emphasis Reid places on our deeply social nature. This shows up in his insistence that testimony is a basic source of knowledge, that some of the mind’s fundamental operations are essentially social, that humans possess a natural language that provides a pre-reflective, preconventional means of communicative interaction, that the meaning of a term is not an idea but the typically public object to which it refers, and that most of our general conceptions are acquired in the course of learning a public language.
Reid insists that the locus of causal power is the agent, and that the self is not merely a material thing being pushed about by laws of nature. Science teaches us about the latter; but such laws are merely the regularities according to which things occur, and it is no part of natural philosophy to inquire into the real, efficient causes of things – that is, the source of motion or change. Our moral and aesthetic judgments are no less objective, and no less capable of truth and falsity, than are our perceptual judgments, and they too are underwritten by first principles. In both his moral and aesthetic theories, Reid relies on comparisons with perception as part of his account of how we acquire the relevant knowledge.