a case in point, for this may be stated in the form "any two and any other two are four," or "any collection formed of two twos is a collection of four." If we can show that such statements as this really deal only with universals, our proposition may be regarded as proved.
One way of discovering what a proposition deals with is to ask ourselves what words we must understand—in other words, what objects we must be acquainted with—in order to see what the proposition means. As soon as we see what the proposition means, even if we do not yet know whether it is true or false, it is evident that we must have acquaintance with whatever is really dealt with by the proposition. By applying this test, it appears that many propositions which might seem to be concerned with particulars are really concerned only with universals. In the particular case of "two and two are four," even when we interpret it as meaning "any collection formed of two twos is a collection of four," it is plain that we can understand the proposition, i.e. we can
