Virtue consists mainly in the avoidance of sin, rather than in anything positive.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“with choosing rightly among possible courses of action.* I am not to blame for not composing an opera, because I don’t know how to do it. The orthodox view is that, wherever two courses of action are possible, conscience tells me which is right, and to choose the other is sin. Virtue consists mainly in the avoidance of sin, rather than in anything positive. There is no reason to expect an educated man to be morally better than an uneducated man, or a clever man than a stupid man. In this way, a number of merits of great social importance are shut out from the realm of ethics.” source