It seems, in short, that when, in such a case, I judge: This surface is not, so far as I can tell, perceptibly different from the one I saw just now, I cannot possibly be judging of the presented object This is not, so far as I can tell, perceptibly different from that object which was presented to me just now, for the simple reason that I can tell, as certainly, almost, as I can tell anything, that it is perceptibly different.