Letters 85.36

Again, the pilot’s art is another’s good—it concerns his passengers just as a physician’s art concerns his patients. But the wise man’s good is a common good—it belongs both to those in whose company he lives, and to himself also. Hence our pilot may perhaps be harmed, since his services, which have been promised to others, are hindered by the storm;

Seneca, Letters to Lucilius 85.36, translated by Richard Mott Gummere