I said, Kripke thinks that the meaning of a proper name is not one or a set of definite descriptions. Looking at Naming and Necessity, we can conclude that he also thinks that the meaning of a proper name is not a property believed or a set of properties believed by a speaker about the referent of that name:
First, the properties believed by the speaker need not be uniquely specifying. Second, even in the case where they are, they may not be uniquely true of the actual referent of the speaker's use but of something else or of nothing. (Kripke 1980, 106)
So the proposal that a proper name’s meaning is simply and only its referent, immediately suggests itself. In this view, since “Hesperus” and “Phosphorus” are coreferential they have the same meaning. Hence (1) and (2) express the same proposition then (1) is knowable a priori because (2) is so. But Kripke doesn’t hold any specific view about the meaning of a proper name and also rejects such a proposal:
So we express this by 'Hesperus is Phosphorus'. Here we're certainly not just saying of an object that it's identical with itself. (Kripke 1980, 28-9)
So he doesn’t hold that (1) and (2) express the same propositions, however he believes that they represent the same state of affairs or facts. For example:
So to speak, the fact, or state of affairs, represented by the statement is the same whether one says “Cicero is an orator” or one says “Tully is an orator.” (Kripke 1971, 140)
We saw, in section II, that Kripke’s rejection of meaning of a proper name (x or y) being a definite description (DD) benefits from the fact that “x is DD” is not analytic. It means that someone expressing “it is possible for x, not being DD” doesn’t contradict herself. So we can conclude that whatever a proper name means (M(x)), it is analytic that “x is M(x)”. Now, since according to Kripke every analytic proposition is also a necessary one, it is necessary that “x is M(x)” therefore x = M(x). Now consider the following argument:
(J) Hesperus = M(Hesperus)
(K) Phosphorus = M(Phosphorus)
(L) Hesperus = Phosphorus
(M) M(Hesperus) = M(Phosphorus)
(M) means that “Hesperus” and “Phosphorus” are synonyms and (1) is analytic and therefore knowable a priori (according to Kripke every analytic propositions is also knowable a priori).
In other words, if Kripke insists to think of (1) as an a posteriori proposition, then he should hold that (1) and (2) are expressing different propositions, but since (1) and (2) represent the same state of affairs, which is thoroughly metaphysical or mind-independent, propositions must have a meaning part, wholly mind-dependant. But, since Hesperus and Phosphorus are the same objects, they share all their metaphysical (or mind-independent) properties. Hence to hold (1) as an a posteriori proposition, “Hesperus” and “Phosphorus” must have a different mind-dependant meaning parts which are true of Venus in every possible worlds (because (1) is necessary). It means that, it should be...