Skeptical Rearmament

Extract

In ‘Skeptism Oisarmed,’ L.S. Carrier asserts the following:

… any reasonable person would accept premise (1) only on the ground that both p and q are propositions for which we can get the requisite evidence.

Premise (1), actually a premise schema attributed to Peter Unger, is the following:

If A both knows p and knows that p entails q, then A can come to know that q.

I suggest, contrary to Carrier's assertion, that many reasonable people, including many philosophers, would regard (1) as a necessary truth knowable a priori, and would be quite happy to accept its universal quantification, with no implied restriction to propositions for which we can get any evidence at all.

How is such a dispute about what reasonable people would do to be resolved? I suggest that, at the very least, Carrier owes us an explanation of the grounds on which he would reject particular instances of the schema, e.g.,