It is not strictly true to say that we understand a proposition p if we know that p is equivalent to “p is true” for this would be the case if accidentally both were true or false. What is wanted is the formal equivalence with respect to the forms of the proposition, i.e., all the general indefinables involved. The sense of an ab function of a proposition is a function of its sense: there || . There are only unasserted propositions. Assertion is merely psychological. If not-p is exactly the same as if it stands alone || In not-p, p is exactly the same as if it stands alone; this point is absolutely fundamental. Among the facts which make “p or q” true there are also facts which make “p and q” true; if propositions do only mean we ought to know such a case, || do only mean, we ought, to know such a case, || have only meaning, we ought, in such a case, to say that these two propositions are identical, but in fact, their sense is different for we have introduced sense by talking of all p's and all q's. Consequently the molecular propositions will only be used in cases where their ab function stands under a generality sign or enters into another function such as “I believe that, etc.,” because then the sense enters.