We must begin by asking; What exactly is common sense? No doubt the word was originally used as a translation of Aristotle's; κοί⋯νη αἴσθησις but that is not its modern meaning. When Reid or more recent philosophers speak of common sense, they clearly have something else in view. At the present day, it is perhaps most often used to mean a quality of a mind, as when we say that jurymen or Members of Parliament should be men of common sense, meaning that they should show intelligence in the ordinary affairs of life; or again, we say that a little common sense would enable us to solve this or that political problem. But we are not concerned with that meaning either, though it would be interesting to discuss it. Common sense, as we are concerned with it here, means rather a body of very general principles commonly accepted by ordinary non-philosophical men in the ordinary affairs of life. These principles are really philosophical—that is to say, they belong to the proper subject-matter of philosophy—but, of course, the plain man who accepts or applies them at every moment of his life is far from being aware of this. Some of them are metaphysical, or (if we prefer to say so) epistemological, others are ethical; and whether or not there can be a common-sense theology, as a recent writer has asserted, it seems quite possible that there may be one or two among them which properly belong to the theologian's province. All these principles, taken together, make up what is usually called the common-sense view of the world. But in this discussion we shall confine ourselves to the metaphysical or epistemological ones, which are more frequently appealed to than the others, and which, besides, seem to be more interesting. But our conclusions, if valid, will apply to the others also.