He may well mean a mechanic qua mechanic is not capable or practising virtue -- not a mechanic qua human being. The ancients tended to predicate formally where

He may well mean a mechanic qua mechanic is not capable or practising virtue -- not a mechanic qua human being. The ancients tended to predicate formally where we predicate materially. When they said 'a mechanic can't practise virtue', they didn't mean every man who is a mechanic, which is what we would mean. They meant every mechanic in so far as he is a mechanic. At least this is the tendency -- I don't know if it applies to this particular case. In this case, it would mean he can't practise virtue, at least not complete virtue, through being a mechanic, but he could in other areas of his life. Jacques Maritain's Introduction to Philosophy explains this helpfully.