It is true that, if certain views which, if I understand them rightly, some Philosophers have seriously entertained, were true ones, it would be quite impossible that any of them should be judgments of perception. For some philosophers seem to me to have denied that we ever do in fact know such things as these, and others not only that we ever know them but also that they are ever true. And, if, in fact, I never do know such a thing, or if it is never true, it will of course, follow that I never perceive such a thing; since I certainly cannot, in this sense, perceive anything whatever, unless I both know it and it is true. But it seems to me a sufficient refutation of such views as these, simply to point to cases in which we do know such things. This, after all, you know, really is a finger: there is no doubt about it: I know it, and you all know it. And I think we may safely challenge any philosopher to bring forward any argument in favour either of the proposition that we do not know it, or of the proposition that it is not true, which does not at some point, rest upon some premiss which is, beyond comparison, less certain than is the proposition which it is designed to attack. The questions whether we do ever know such things as these, and whether there are any material things, seem to me, therefore, to be questions which there is no need to take seriously: they are questions which it is quite easy to answer, with certainty, in the affirmative. What does, I think, need to be taken seriously, and what is really dubious, is not the question, whether this is a finger, or whether I know that it is, but the question _what,_ in certain respects, I am knowing, when I know that it is. And this is the question to which I will now address myself. To begin with there is one thing which seems to me to be very certain indeed about such judgments. It is unfortunately a thing which I do not know how properly to express. There seem to me to be objections to every way of expressing it which I can think of. But I hope I may be able to make my meaning clear, in spite of the inadequacy of my expression. The thing I mean is a thing which may to some people seem so obvious as to be scarcely worth saying. But I cannot help thinking that it is not always clearly recognised, and even that some philosophers, to judge from what they say, might perhaps dispute it. It seems to me to be an assumption which is silently made in many treatments of the subject, and, as I say, it seems to me to be very certain indeed. But I think it is at all events worth while to try to make the assumption explicit, in case it should be disputed. If it really is not true, then the other questions to which I shall go on, and which seem to me really dubious and difficult, do not, I think, arise at all.