There are
internal
relations between one
proposition
& another; but a
proposition
cannot have to another
the internal relation
which a
name has to the
proposition of
which it is a constituent,
&
which ought to be meant by saying it
‘occurs’ in it. In this sense one
proposition can't
‘occur’ in another.
Internal relations are relations between types,
which can't be expressed in
propositions, but are all shewn in the
symbols themselves, & can be exhibited systematically in
tautologies. Why we come to call them
‘relations
’ is because logical
propositions have
|| an analogous relation to them,
to
that which properly relational
propositions have to relations.
Propositions can have many
different internal relations to one another.
The
one
which entitles us to deduce
one from another, is that if say, they are
φa
& φa ⊃ ψa, then
φa
. φa ⊃ ψa : ⊃ :
ψa is a tautology.
The symbol of identity expresses
the internal relation between a function & its argument:
i.e. φa
=
(∃x)φx.x = a.