Reality Check
Penultimate Amazing
So you cannot prove your statement? Then it is an assumption. And since it has absolutely no consequences then it is useless.It uses Interactions between Relations and Elements, and this is not a proof but the Minimal Accepted Form that enables to define some interesting axiomatic system, in the first place.
MAF is a pre-axiomatic form where also Relations (unlike in axiomatic systems) have no meaning of their own (in addition to Elements).
By asking about a proof you simply show that you (still) do not get axiomatic of pre-axiomatic frameworks.