John Calvin Commentary Romans 2:19

"and art confident that thou thyself art a guide of the blind, a light of them that are in darkness," — Romans 2:19 (ASV)

And believest yourself, etc. More is still granted to them, as though they had not only what was sufficient for themselves, but also that with which they could enrich others. He grants, indeed, that they had such an abundance of learning that others might have been supplied.