Perhaps there is some simple and satisfactory answer, which has escaped me, that such philosophers could give to all my questions; but I cannot help thinking that assumptions as to the nature of material things have too often been made, without its even occurring to those who made them to ask, what, if they were true, we could be judging when we make such judgments as these; and that, if this question had been asked, it would have become evident that those assumptions were far less certain than they appeared to be.