4.53 The general propositional form is a variable.


5 A proposition is a truth-function of elementary propositions. (An
elementary proposition is a truth-function of itself.)


5.01 Elementary propositions are the truth-arguments of propositions.


5.02 The arguments of functions are readily confused with the affixes of
names. For both arguments and affixes enable me to recognize the meaning of
the signs containing them. For example, when Russell writes '+c', the 'c'
is an affix which indicates that the sign as a whole is the addition-sign
for cardinal numbers. But the use of this sign is the result of arbitrary
convention and it would be quite possible to choose a simple sign instead
of '+c'; in 'Pp' however, 'p' is not an affix but an argument: the sense of
'Pp' cannot be understood unless the sense of 'p' has been understood
already. (In the name Julius Caesar 'Julius' is an affix. An affix is
always part of a description of the object to whose name we attach it: e.g.
the Caesar of the Julian gens.) If I am not mistaken, Frege's theory about
the meaning of propositions and functions is based on the confusion between
an argument and an affix. Frege regarded the propositions of logic as
names, and their arguments as the affixes of those names.


5.1 Truth-functions can be arranged in series. That is the foundation of
the theory of probability.