This, I think, was clearly one of Hume's views. He meant to fix the limits of our knowledge at a point which would _exclude_ most religious propositions and a great many philosophical ones, as incapable of being known; but which would _include_ all the other kinds of propositions, which are most universally accepted by common-sense, as capable of being known. And he thought that, so far as matters of fact beyond the reach of our personal observation are concerned, this point coincided with that at which the possibility of "foundation on experience" ceases. But, if we turn to another part of his work, we find a very different view suggested. In a quite distinct section of both his books, he investigates the beliefs which we entertain concerning the existence of "external objects." And he distinguishes two different kinds of belief which may be held on this subject. "Almost all mankind, and philosophers themselves, for the greatest part of their lives," believe, he says, that "the very things they feel and see" _are_ external objects, in the sense that they continue to exist, even when we cease to feel or see them. Philosophers, on the other hand, have been led to reject this opinion and to suppose (when they reflect) that what we actually perceive by the senses never exists except when we perceive it, but that there are other external objects, which do exist independently of us, and which _cause_ us to perceive what we do perceive. Hume investigates both of these opinions, at great length in the _Treatise_, and much more briefly in the _Enquiry_, and comes to the conclusion, in both books, that neither of them can be "founded on experience," in the sense he has defined. As regards the first of them, the vulgar opinion, he does seem to admit in the _Treatise_ that it is, in a sense, founded on experience; but not, he insists, in the sense defined. And he seems also to think that, apart from this fact, there are conclusive reasons for holding that the opinion cannot be true. And as regards the philosophical opinion, he says that any belief in external objects, which we never perceive but which cause our perceptions, cannot possibly be founded on experience, for the simple reason that if it were, we should need to have directly observed some of these objects and their "conjunction" with what we do perceive, which _ex hypothesi,_ we cannot have done, since we never do directly observe any external object.