3.341 The essential in a proposition is thus that which all propositions that can express the same sense have in common.
And likewise in general the essential in a symbol is that which all symbols that can fulfill the same purpose have in common.
What is common to all propositions that can express the same sense? The ability to express just that sense. Must this ability depend on some other common feature? Not that I can see. The same goes for symbols. So 3.341 seems to be quite empty, its only purpose being to confirm the suspicion about 3.34 that it was not an important metaphysical truth.