6.1221 If, e.g., two propositions “p” and “q” in the combination “p → q” give a tautology, then it is clear that q follows from p.

That, e.g., “q” follows from “p → q . p”, we see from these two propositions themselves, but we can also see it by combining them into “p → q . p:→ : q” and now showing that this is a tautology.

OK