The only case in which it might seem, at first sight, as if our proposition were untrue, is the case in which an a priori proposition states that all of one class of particulars belong to some other class, or (what comes to the same thing) that all particulars having some one property also have some other. In this case it might seem as though we were dealing with the particulars that have the property rather than with the property. The proposition “two and two are four” is really 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.