M. Tullius Cicero, De Officiis
Walter Miller, Ed.

[30] Now since we have set forth the two kinds of¹ injustice and assigned the motives that lead to each, and since we have previously established the principles by which justice is constituted, we shall be in a position easily to decide what our duty on each occasion is, unless we are extremely self-centred; for indeed it is not an easy matter to be really concerned with other people's affairs; and yet in Terence's play, we know, Chremes “thinks that nothing that concerns man is foreign to him.” Nevertheless, when things turn out for our own good or ill, we realize it more fully and feel it more deeply than when the same things happen to others and we see them only, as it were, in the far distance; and for this reason we judge their case differently from our own. It is, therefore, an excellent rule that they give who bid us not to do a thing, when there is a doubt whether it be right or wrong; for righteousness shines with a brilliance of its own, but doubt is a sign that we are thinking of a possible wrong.