Alfred Tarski in his next study (Some Methodological Investigations on the definability of concepts, TARSKI, Logic, Semantics, Metamathematics. Papers from 1923 to 1938. Clarendon Press, Oxford, 1956, 296-308.) describes the parallelism between concepts and theorems:
axiom - primitive concept,
theorem - defined concept,
proof and its rules - definition and its rules.
I always thought this was mysterious, and I might have noticed myself.
My question would be that, apart from Tarski's study, there are other sources, research in this direction. Or what could be the deeper reason for far-reaching parallelism?