When we say of a prop. of form aRb that what symbolises is that ‘a’ “R” is between “a” & “b”, it must be remembered that in fact the prop. is capable of further analysis because a, R, & b are not simples. But what seems certain is that when we have analysed , it, we shall in the end come to props. of the same form in respect of the fact that they do consist in one thing being between 2 others.
How can we talk of the general form of a proposition, without knowing any simples or any unanalysable props. ˇin which particular names & relations occur? What justifies us in doing this is that though we don't know any unanalysable props. ˇof this kind yet we can understand ˇwhat is meant by a prop. of the form (∃x,y,R). xRy ˇ(which is unanalysable), even though we know

no props. of the form xRy.
If you had any unanalysable prop. in which particular names & relations occurred (and unanalysable prop. = one in which the only fundamental symbols = ones not capable of definition, occur) then you always can form from it a prop. of form (∃x,y,R). xRy, which though it contains no particular names & relations, is unanalysable.

(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.