5.475 All that is required is that we should construct a system of signs
with a particular number of dimensions--with a particular mathematical
multiplicity


5.476 It is clear that this is not a question of a number of primitive
ideas that have to be signified, but rather of the expression of a rule.


5.5 Every truth-function is a result of successive applications to
elementary propositions of the operation '(-----T)(E, ....)'. This
operation negates all the propositions in the right-hand pair of brackets,
and I call it the negation of those propositions.


5.501 When a bracketed expression has propositions as its terms--and the
order of the terms inside the brackets is indifferent--then I indicate it
by a sign of the form '(E)'. '(E)' is a variable whose values are terms of
the bracketed expression and the bar over the variable indicates that it is
the representative of ali its values in the brackets. (E.g. if E has the
three values P,Q, R, then (E) = (P, Q, R). ) What the values of the
variable are is something that is stipulated. The stipulation is a
description of the propositions that have the variable as their
representative. How the description of the terms of the bracketed
expression is produced is not essential. We can distinguish three kinds of
description: 1.Direct enumeration, in which case we can simply substitute
for the variable the constants that are its values; 2. giving a function fx
whose values for all values of x are the propositions to be described; 3.
giving a formal law that governs the construction of the propositions, in
which case the bracketed expression has as its members all the terms of a