The man whose virtue has no source except a purely terrestrial prudence will, in such a world, become an adventurer if he has the courage, and, if not, will seek obscurity as a timid time-server.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“no point in steadfast adherence to a cause, when no cause is important or has a chance of stable victory; no argument in favour of truthfulness, when only supple tergiversation makes the preservation of life and fortune possible. The man whose virtue has no source except a purely terrestrial prudence will, in such a world, become an adventurer if he has the courage, and, if not, will seek obscurity as a timid time-server. Menander, who belongs to this age, says: So many cases I have known Of men who, though not naturally rogues, Became so, through misfortune, by constraint. This sums up the moral character of the third century B.C., except for a few exceptional men.” source