There are internal relations between one prop. & another; but a prop. cannot have to another the internal relation wh. a name has to the prop. it o of wh. it is a constituent, & wh. ought to be meant by saying it ‘occurs’ in it. In this sense one prop. can't ‘occur’ in another.
Internal relations are relations between types, wh. can't be expressed in props., but are all shewn in the symbols themselves, & can be exhibited systematically in tautologies. Why we come to call them ‘relations’ is because logical props. have

an analogous
the same

relation to them, ˇto that which have real properly relational props. have to relations.
Props. can have many different internal relations to one another. The one wh. entitles us to deduce the one from another, is that if put in expressed in say, they are φa & , φa ⊃ ψa, then φa . φa ⊃ ψa : ⊃ : ψa is a tautology.
Ide The symbol of identity expresses the internal relation between a function & its argument: i.e. φa = (∃x)φx.x = a.

(2015–) Wittgenstein Source Bergen Nachlass Edition (WS-BNE). Edited by the Wittgenstein Archives at the University of Bergen under the direction of Alois Pichler. In: Wittgenstein Source, curated by Alois Pichler (2009–) and Joseph Wang-Kathrein (2020–). (N) Bergen: WAB.