What, then, is it that may sometimes give room for a doubt and seem to call for consideration? It is, I believe, when a question arises as to the character of an action under consideration. *19* For it often happens, owing to exceptional circumstances, that what is accustomed under ordinary circumstances to be considered morally wrong is found not to be morally wrong. For the sake of illustration, let us assume some particular case that admits of wider application: what more atrocious crime can there be than to kill a fellow-man, and especially an intimate friend? But if anyone kills a tyrant--be he never so intimate a friend--he has not laden his soul with guilt, has he? The Roman People, at all events, are not of that opinion; for of all glorious deeds they hold such an one to be the most noble. Has expediency, then, prevailed over moral rectitude? Not at all; moral rectitude has gone hand in hand with expediency. #Need of a rule for guidance.# Some general rule, therefore, should be laid down to enable us to decide without error, whenever what we call the expedient seems to clash with what we feel to be morally right; and if we follow that rule in comparing courses of conduct, we shall never swerve from the path of duty. *20* That rule, moreover, shall be in perfect harmony with the Stoics' system and doctrines. It is their teachings that I am following in these books, and for this reason: the older Academicians and your Peripatetics (who were once the same as the Academicians) give what is morally right the preference over what seems expedient; and yet the discussion of these problems, if conducted by those who consider whatever is morally right also expedient and nothing expedient that is not at the same time morally right, will be more illuminating than if conducted by those who think that something not expedient may be morally right and that something not morally right may be expedient. But our New Academy allows us wide liberty, so that it is within my right to defend any theory that presents itself to me as most probable. But to return to my rule.