Thomas Reid (April 26, 1710 – October 7, 1796), Scottish philosopher, and a contemporary of David Hume, was the founder of the Scottish School of Common Sense, and played an integral role in the Scottish Enlightenment. The early part of his life was spent in Aberdeen, Scotland, where he created the 'Wise Club' (a literary-philosophical association) and graduated from the University of Aberdeen. He was given a professorship at King's College, Aberdeen in 1752, where he wrote An Inquiry Into the Human Mind on the Principles of Common Sense (published in 1764). Shortly afterward he was given the prestigious Professorship of Moral Philosophy at the University of Glasgow when he was called to replace Adam Smith. He resigned from this position in 1781.

Reid believed that common sense (in a special philosophical sense) is, or at least should be, at the foundation of all philosophical inquiry. He disagreed with Hume and George Berkeley, who asserted that humans do not experience matter or mind as either sensations or ideas. Reid claimed that common sense tells us that there is matter and mind.

In his day and for some years into the 19th century, he was regarded as more important than David Hume. He advocated direct realism, or common sense realism, and argued strongly against the Theory of Ideas advocated by John Locke, René Descartes, and (in varying forms) nearly all Early Modern philosophers who came after them. He had a great admiration for Hume and asked him to correct the first manuscript of his (Reid's) Inquiry.

His theory of knowledge had a strong influence on his theory of morals. He thought epistemology was an introductory part to practical ethics: When we are confirmed in our common beliefs by philosophy, all we have to do is to act according to them, because we know what is right. His moral philosophy is reminiscent of the Latin stoicism mediated by the scholastics, St. Thomas Aquinas and the Christian way of life. He often quotes Cicero, from whom he adopted the term "sensus communis."

He set down six axioms which he regarded as an essential basis for reasoning, all derived from "sensus communis":

*That the thoughts of which I am conscious are thoughts of a being which I call myself, my mind, my person; *That those things did really happen that I distinctly remember; *That we have some degree of power over our actions, and the determination of our will; *That there is life and intelligence in our fellow men with whom we converse; *That there is a certain regard due to human testimony in matters of fact, and even to human authority in matters of opinion; *That, in the phenomena of nature, what is to be, will probably be like what has been in similar circumstances.

These axioms did not so much answer the testing problems set by David Hume and, earlier, René Descartes, as simply deny them. Contemporary philosopher Roy Sorensen writes "Reid's common sense looks like an impression left by Hume; concave where Hume is convex, convex where Hume is concave. One explanation is that common sense is reactive... Without a provocateur, common sense is faceless."

His reputation waned after attacks on the Scottish School of Common Sense by Immanuel Kant and John Stuart Mill, but his was the philosophy taught in the colleges of North America, during the 19th century, and was championed by Victor Cousin, a French philosopher. Justus Buchler showed that Reid was an important influence on the American philosopher C.S. Peirce, who shared Reid's concern to revalue common sense and whose work links Reid to pragmatism. To Peirce, the closest we can get to truth in this world is a consensus of millions that something is so. Common sense is socially constructed truth, open to verification much like scientific method, and constantly evolving as evidence, perception, and practice warrant. Reid's reputation has revived in the wake of the advocacy of common sense as a philosophical method or criterion by G. E. Moore early in the 20th century, and more recently due to the attention given to Reid by contemporary philosophers, in particular those seeking to defend Christianity from philosophical attacks, such as William Alston and Alvin Plantinga.

He wrote a number of important philosophical works, including Inquiry into the Human Mind on the Principles of Common Sense (1764, Glasgow & London), Essays on the Intellectual Powers of Man (1785) and Essays on the Active Powers of Man (1788). In 1844, Schopenhauer praised Reid for explaining that the perception of external objects does not result from the raw data that is received through the five senses:

*Philosophy of perception * Stephen Barker & Tom Beauchamp, eds., "Thomas Reid: Critical Interpretations" (1976). * Steffen Ducheyne, Reid’s Adaptation and Radicalization of Newton’s Natural Philosophy, History of European Ideas 32, 2006, pp. 173-189. * Davis, William C., Thomas Reid’s Ethics: Moral Epistemology on Legal Foundations, Continuum International, 2006. ISBN 0-826488-09-9

*The Aberdeen University Reid Project *Stanford Encyclopedia of Philosophy entry on Reid *Inquiry into the Human Mind, Essays on the Active Powers of Man (1, 2 and 4), and Essays on the Intellectual Powers of Man *Reid @ Google Books