On the single axioms of protothetic. III.
Bolesław Sobociński · Notre Dame Journal of Formal Logic · 1961
BOLESkAW SOBOCINSKI §6*.When in 1938 I proved that condition b of metarule L follows from the remaining conditions α and c , I also remarked that probably condition α of L could be weakened too.Viz., I thought that system .S could be substituted by a suitable fragment of it, and that this would certainly be done, if we had at our disposal SHI, which as we remember enables us to make extensional deductions for expressions belonging to the semantical category of propositions.This suggestion of mine and the result concerning the redundancy of condition b enabled Lesniewski to construct his axiom A : Âm [p q]\\p=q.=:.: