6.1221

If for example two propositions “p” and “q” give a tautology in the connexion “p⊃q”, then it is clear that q follows from p. E.g. that “q” follows from “p⊃q.p” we see from these two propositions themselves, but we can also show it by combining them to “p⊃q.p:⊃:q” and then showing that this is a tautology.