And, if we agree to use the term in this sense, then it is obvious that no more can be necessary for the truth of the assertion that there are material things, than is necessary for the truth of judgments of the kind with which I propose to deal. But no more can be necessary for the truth of these judgments than is actually asserted in or logically implied by them. And if we approach the question what is necessary for the truth of the assertion that there are material things, by asking what it is that we actually assert when we make such judgments as these, certain reasons for doubting how much is necessary are, I think, brought out much more clearly, than if we approach the question in any other way. Many philosophers have told us a very great deal as to what they suppose to be involved in the existence of material things; and some, at least, among them seem to have meant by "material things" such things as inkstands, fingers and clouds. But I can think of only one type of view as to the constitution of material things, which is such that it is tolerably clear what answer those who hold it would give to the simple question; What is it that I am judging, when I judge, as I now do, that that is an inkstand? The type of view I mean is that to which the view that Mill suggests, when he explains what he means by saying that Matter is a Permanent Possibility of Sensation, and also the view or views which Mr. Russell seems to suggest in his "Our Knowledge of the External World," seem to belong. In the case of views of this kind, it is, I think, tolerably clear what answer those who hold them would give to _all_ the questions I want to raise about judgments of the kind I have described. But it does not seem to me at all certain that any view of this type is true; and certainly many philosophers have held and do hold that all views of this type are false. But in the case of those who do hold them to be false, I do not know, in any single case, what answer would be given to _all_ the questions which I want to raise. In the case of philosophers, who do not accept any view of the Mill-Russell type, none, so far as I know, has made it clear what answer he would give to _all_ my questions: some have made it clear what answer they would give to _some_ of them; but many, I think, have not even made it clear what answer they would give to any. Perhaps there is some simple and satisfactory answer, which has escaped me, that such philosophers could give to all my questions; but I cannot help thinking that assumptions as to the nature of material things have too often been made, without its even occurring to those who made them to ask, what, if they were true, we could be judging when we make such judgments as these; and that, if this question had been asked, it would have become evident that those assumptions were far less certain than they appeared to be.