It is obvious, indeed, that if any interpretation on these lines _is_ the only true interpretation of our five propositions, none of those which I have vaguely suggested comes anywhere near to expressing it in its ultimate form. They cannot do so for the simple reason that, in them, the conditions under which I _should_ experience certain other sensibles are themselves expressed in terms of _physical objects,_ and not in terms of sensibles and our experience of them. The conditions are expressed in such terms as "if I were to move my body," "if I were to look straight at the coins," "if I were to turn the coins over," etc.; and all these are obviously propositions, which must themselves again be interpreted in terms of sensibles, if our original five propositions need to be so. It is obvious, therefore, that any _ultimate_ interpretation of our five propositions, on these lines, would be immensely complicated; and I cannot come anywhere near to stating exactly what it would be. But it seems to me possible that _some_ such interpretation could be found, and that it is the _only_ true one.
The great recommendation of this view seems to me to be that it enables us to see, more clearly than any other view can, how our knowledge of physical propositions can be based on our experience of sensibles, in the way in which principle (_β_) asserts it to be. If, when I know that the coins are round, all that I know is some such thing as that if, after experiencing the sensibles I do now experience, I were to experience still others, I should finally experience a third set, we can understand, as clearly as we can understand how any knowledge can be obtained by induction at all, how such a knowledge could be based on our previous experience of sensibles, and how it could be verified by our subsequent experience.
On the other hand, apart from the difficulty of actually giving any interpretation on these lines, which will meet the requirements, the great objection to it seems to me to be this. It is obvious that, on this view, though we shall still be allowed to say that the coins _existed_ before I saw them, are _circular_ etc., all these expressions, if they are to be true, will have to be understood in a Pickwickian sense. When I know that the coins existed before I saw them, what I know will not be that anything whatever existed at that time, in the sense in which those elliptical patches of colour exist now. _All_ that I know will be simply that, since the elliptical patches exist now, it is true, that, _if_ certain unrealised conditions had been realised, I should have had certain sensations that I have not had; or, _if_ certain conditions, which may or may not be realised in the future, were to be so, I _should_ have certain experiences. Something like this will actually be the _only true_ thing that can be meant by saying that the coins existed before I saw them. In other words, to say of a _physical object_ that it _existed_ at a given time will always consist merely in saying of some sensible, _not_ that _it_ existed at the time in question, but something quite different and immensely complicated. And thus, though, when I know that the coins exist, what I know will be merely some proposition about these sensibles which I am directly apprehending, yet this view will not contradict principle (_a_) by _identifying_ the coins with the sensibles. For it will say that to assert a given thing of the _coins_ is not equivalent to asserting the _same thing_ of the sensibles, but only to asserting of them something quite different.