Jowett: quality of the soul

Soc. If then virtue is a quality of the soul, and is admitted to be profitable, it must be wisdom or prudence, since none of the things of the soul are either profitable or hurtful in themselves, but they are all made profitable or hurtful by the addition of wisdom or of folly ; and therefore and therefore if virtue is profitable, virtue must be a sort of wisdom or prudence ? MENO