The question whether a
proposition has
sense || Sinn can never depend on the
truth of another
proposition
about a constituent of the first.
E.g. the question whether
(x). x = x has
meaning || Sinn
can't depend on the question whether
(∃x). x = x is
true. It doesn't describe reality at
all, & deals therefore solely with symbols;
it says that they must
symbolise,
but not
what they symbolise.
It's obvious that the dots
& brackets are symbols, & obvious also that they
haven't any
independent meaning. You
must therefore, in order to introduce so
-called “logical
constants” properly, introduce the general notion of
all
possible combinations of them
= the general form of
a proposition
You thus introduce both a–b functions, identity
& universality (the 3 fundamental constants)
simultaneously.