Now these philosophers may be right in holding this. It may, perhaps, be true that, in this sense, my own observations give me no reason whatever for believing that any other person ever has or will perceive anything like or unlike what I perceive. But I think it is desirable we should realise how paradoxical are the consequences which must be admitted, if this is true. It must then be admitted that the very large part of our knowledge, which we suppose to have some basis in experience, is by no means based upon experience, in the sense, and to the extent, which we suppose. We do for instance, commonly suppose that there is some basis in experience for the assertion that some people, whom we call Germans, use one set of words to express much the same meaning which we express by using a different set of words. But, if this view be correct, we must admit that no person's experience gives him any reason whatever for supposing that, when he hears certain words, any one else has ever heard or thought of the same words, or meant anything by them. The view admits, indeed, that I do know that when I hear certain words, somebody else has generally had thoughts more or less similar to those which I suppose him to have had: but it denies that my own observations could ever give me the least reason for supposing that this is so. It admits that my own observations may give me reason for supposing that _if_ anyone has ever had perceptions like mine in some respects, he will also have had other perceptions like others of mine: but it denies that they give me any reason for supposing that any one else has had a perception like one of mine. It admits that my own observations may give me reason for supposing that certain perceptions and thoughts in _one_ person (_if_ they exist) will be followed or preceded by certain other perceptions and thoughts in that person: but it denies that they give me any reason whatever for _any_ similar generalisation concerning the connection of a certain kind of perception in one person with a certain kind of perception in another. It admits that I should not have certain perceptions, which I do have, unless someone else had had certain other perceptions; but it denies that my own observations can give me any reason for saying so--for saying that I should not have had this perception, unless someone else had had that. No observations of mine, it holds, can ever render it probable that such a generalisation is true; no observation of mine can ever confirm or verify such a generalisation. If we are to say that any such generalisation whatever is based upon observation, we can only mean, what Reid means, that it is based on a series of assumptions. When I observe this particular thing, I assume that _that_ particular thing, which I do not observe, exists; when I observe another particular thing, I again assume that a second particular thing, which I do not observe, exists; when I observe a third