Thomas Reid - Thomas Reid's Theory of Common Sense

Thomas Reid's Theory of Common Sense

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 Latin stoicism in its emphasis on the agency of the subject and self-control. He often quotes Cicero, from whom he adopted the term "sensus communis". Reid's answer to Hume's skeptical and naturalist arguments was to enumerate a set of principles of common sense (sensus communis) which constitute the foundations of rational thought. Anyone who undertakes a philosophical argument, for example, must implicitly presuppose certain beliefs like, "I am talking to a real person," and "There is an external world whose laws do not change," among many other positive, substantive claims. For Reid, the belief in the truth of these principles is not rational; rather, reason itself demands these principles as prerequisites, as does the innate "constitution" of the human mind. It is for this reason (and possibly a mocking attitude toward Hume and Berkeley) that Reid sees belief in the principles of common sense as a litmus test for sanity. For example, in The Intellectual Powers of Man he states, "For, before men can reason together, they must agree in first principles; and it is impossible to reason with a man who has no principles in common with you." One of the first principles he goes on to list is that "qualities must necessarily be in something that is figured, coloured, hard or soft, that moves or resists. It is not to these qualities, but to that which is the subject of them, that we give the name body. If any man should think fit to deny that these things are qualities, or that they require any subject, I leave him to enjoy his opinion as a man who denies first principles, and is not fit to be reasoned with."

Reid also made positive arguments based in phenomenological insight to put forth a novel mixture of direct realism and ordinary language philosophy. In a typical passage in the Intellectual Powers he asserts that when he has a conception of a centaur, the thing he conceives is an animal, and no idea is an animal; therefore, the thing he conceives is not an idea, but a centaur. This point relies both on an account of the subjective experience of conceiving an object and also on an account of what we mean when we use words. Because Reid saw his philosophy as publicly accessible knowledge, available both through introspection and the proper understanding of how language is used, he saw it as the philosophy of common sense.