6.2322 The identity of the meaning [Bedeutung] of two expressions cannot be asserted [maintained, contended]. Because in order to be able to assert something about their meaning, I must be acquainted with their meaning: and in being acquainted with their meaning, I know whether the meaning is the same or different.

So in some sense I cannot say [“maintain” is another possible translation of behaupten] “The Morning Star” refers to the same thing [has the same Bedeutung] as “the Evening Star.” That is, I cannot hold or prove that this is a fact. “Facts” about expressions are tautologies, matters of definition, not contentions.