"A great human philosopher ... said that where Virtue is concerned 'Experience is the mother of illusion'..."
Do we know perhaps who this great philosopher might be?
I am sometimes having difficulty discrening, when Screwtape quotes a "great", or "sensible", or [insert favorable adjective here] human, whether this is a human that Lewis himself is in sympathy with, or is someone that Lewis imagines that Screwtape would approve of. GBS seems to be firmly in the latter camp, and Boethius in the former, so we have to examine them on a case-by-case basis.