did happen, Q would be falsified. Thus we indicate the meaning of Q (or P) by describing facts which make Q true, and other facts that would make it false. If facts of the latter kind occurred our world would be rather different from the one in which we are actually living; the properties of the 'data' would depend on other human bodies (or perhaps only one of them) as well as upon the body M.
This fictitious world may be empirically impossible, because incompatible with the actual laws of nature — though we cannot at all be sure of this — but it is logically possible, because we were able to give a description of it. Now let us for a moment suppose this fictitious world to be real. How would our language adapt itself to it ? It might be done in two different ways which are of interest for our problem.
Proposition P would be false. As regards Q, there would be two possibilities. The first is to maintain that its meaning is still to be the same as that of P. In this case Q would be false and could be replaced by the true proposition, T can feel somebody else's pain as well as my own.' (R) R would state the empirical fact (which for the moment we suppose to be true) that the datum 'pain' occurs not only when M is hurt, but also when some injury is inflicted upon some other body, say, the body 'O'.
If we express the supposed state of affairs by the proposition R, there will evidently be no temptation and no pretext to make any' solipsistic' statement. My body — which in this case could mean nothing but 'body M' — would still be unique in that it would always appear in a particular perspective (with invisible back, etc.), but it would no longer be unique as being the only body upon whose state depended the properties of all other data. And it was only this latter characteristic which gave rise to the egocentric view.
The philosophic doubt concerning the 'reality of the external world' arose from the consideration that I had no knowledge of that world except by perception, i.e., by means of the sensitive organs of my body. If this is no longer true, if the data depend also on other bodies O (which differ from M in certain empirical respects, but not in principle), then there will be no more justification in calling the data 'my own'; other individuals O will have the same right to be regarded as owners or proprietors of the data. The sceptic was afraid that other bodies might be nothing but images
