Thomas Reid is justly famous for his critique of the metaphysics, epistemology, and psychology of his influential predecessors and overlapping contemporaries. Debate continues about the success of his critique, but the philosophical intelligence displayed in his dissection of the faults in “the way of ideas” common to such otherwise disparate thinkers as Descartes, Locke, and Hume is beyond doubt. Indeed, Reid's critique is an exemplary piece of philosophical art in that it aims to detect a central flaw in the underpinnings of a great enterprise. It exhibits the “subtle but well balanced intellect” that was later praised by C. S. Peirce. But this very achievement has tended to obscure some of Reid's more positive contributions to philosophy. Of course, his defense of common sense and his elaboration of what it means have been subject to plenty of critical attention, but there are many other areas in which Reid developed creative and original positions that have been relatively neglected in the literature. In what follows, I shall expound and discuss one that has been largely ignored both in its general form and in its particular applications.

The idea in question is that of “the social operations of mind.” Reid develops this idea both in his Inquiry and in the Essays and deploys it in his discussion of a number of important topics, most notably those of promising and testimony.