Russell's paradox.


3.334 The rules of logical syntax must go without saying, once we know how
each individual sign signifies.


3.34 A proposition possesses essential and accidental features. Accidental
features are those that result from the particular way in which the
propositional sign is produced. Essential features are those without which
the proposition could not express its sense.


3.341 So what is essential in a proposition is what all propositions that
can express the same sense have in common. And similarly, in general, what
is essential in a symbol is what all symbols that can serve the same
purpose have in common.


3.3411 So one could say that the real name of an object was what all
symbols that signified it had in common. Thus, one by one, all kinds of
composition would prove to be unessential to a name.


3.342 Although there is something arbitrary in our notations, this much is
not arbitrary--that when we have determined one thing arbitrarily,
something else is necessarily the case. (This derives from the essence of
notation.)