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Thomas Reid (1710–1796)

Reid argued that Hume’s skepticism — the denial that we can know the external world, that causation is real, or that the self persists over time — is not a discovery about the limits of knowledge but a reductio ad absurdum of the philosophical tradition that produced it. The tradition, from Descartes through Locke to Hume, assumes that the mind has direct access only to its own ideas (sense impressions, perceptions) and must infer the external world from them. Reid rejected the assumption: perception gives us direct access to the external world, not to ideas that represent it. The “theory of ideas” — the claim that we perceive only our own mental representations — is what generates the skeptical problems; reject the theory, and the problems dissolve. Common sense — the framework of beliefs that all human beings share and that philosophy cannot coherently deny — is not a philosophical embarrassment but the starting point of inquiry.

Life

Born 26 April 1710 in Strachan, Kincardineshire, Scotland, to a family of Presbyterian ministers. Educated at Marischal College, Aberdeen (MA, 1726). Minister in the Church of Scotland at New Machar (1737–52). Regent (a teaching position covering all subjects) at King’s College, Aberdeen (1752–64), where he founded the Aberdeen Philosophical Society (the “Wise Club”) and developed the common-sense philosophy in response to Hume’s Treatise. Professor of moral philosophy at the University of Glasgow (1764–80), succeeding Adam Smith — who had left for the tutoring appointment with the Duke of Buccleuch.

Reid corresponded with Hume and admired him personally while rejecting his conclusions. He sent Hume a draft of his Inquiry into the Human Mind (1764) before publication; Hume responded courteously but was not persuaded. Reid retired from teaching in 1780 and spent his remaining years writing the Essays (1785, 1788). Died 7 October 1796 in Glasgow.

Common-sense philosophy

An Inquiry into the Human Mind on the Principles of Common Sense (1764) and the Essays on the Intellectual Powers of Man (1785) and Essays on the Active Powers of the Human Mind (1788) develop the position.

The rejection of the theory of ideas. Locke held that perception is indirect: we perceive our own ideas (mental representations), which are caused by external objects. Hume radicalised this: if all we have are ideas, we cannot prove that external objects exist, that causation is real, or that the self persists. Reid argued that the problem lies in the premise, not in the conclusion. Perception is direct: when I see a tree, I perceive the tree, not an idea of the tree. The theory of ideas generates skepticism because it interposes a mental intermediary between the perceiver and the world; remove the intermediary, and the skeptical problems do not arise.

Common sense as first principles. Reid argued that certain beliefs are held universally, cannot be proved (because any proof would have to rely on something less certain than the beliefs themselves), and cannot be coherently denied (because denying them undermines the conditions of rational discourse). The existence of the external world, the reliability of memory, the uniformity of nature, the existence of other minds — these are common-sense beliefs that philosophy must accept as starting points rather than attempting to prove or disprove.

Direct realism. Perception provides direct, non-inferential access to the external world. This is not naive realism (the claim that things are exactly as they appear); Reid acknowledged that perception involves complex physiological processes. But the output of perception is a direct awareness of external objects, not an awareness of internal representations from which external objects must be inferred.

Where Reid stops

The common-sense philosophy was influential in the eighteenth and nineteenth centuries (particularly in Scottish and American academic philosophy) but was marginalised by Kant’s critical philosophy, which offered a more systematic response to Hume that did not rely on the appeal to common sense. Kant argued that the mind structures experience through the categories of the understanding — a position that explains how knowledge is possible without either Hume’s skepticism or Reid’s appeal to self-evident first principles. Whether Kant’s response supersedes Reid’s or is a different solution to the same problem is debated; G. E. Moore’s twentieth-century “defence of common sense” and Wittgenstein’s On Certainty (1969) have revived interest in Reidian themes from within analytic philosophy.

The “first principles” are presented as self-evident, but which beliefs count as first principles is not determined by a criterion Reid can specify. The list is generated by introspection and consensus rather than by argument, and different philosophers have different intuitions about what is self-evident. The charge of conservatism — that common-sense philosophy immunises existing beliefs against philosophical challenge by declaring them first principles — has been pressed since Hume’s time. Reid would respond that the charge applies only if common sense is treated as dogma; properly understood, common sense is the shared starting point from which inquiry begins, not a set of conclusions it cannot reach.

Key works

See also: Hume · Locke · Wittgenstein