Prawitz conjectured that the proof-theoretically valid logic is intuitionistic logic. Recent work
on proof-theoretic validity has disproven this. In fact, it has been shown that proof-theoretic
validity is not even closed under substitution. In this paper, we make a minor modification to
the definition of proof-theoretic validity found in paper 'Towards a foundation of a general
proof theory'and refined by Schroeder-Heister in 'Validity concepts in proof-theoretic
semantics'. We will call the new notion generalized proof-theoretic validity and show that the …