The following is an excerpt from Jonsen and Toulmin's book, The Abuse of Casuistry. It places Cicero at the origin of some contemporay approaches to issues in Applied Ethics.

In book III of his essay, On Duties (De Officiis), he described a number of examples in which individuals are perplexed by a conflict of moral duty. Some of these are invented cases that became staples of moral debate: for example, the shipwrecked companions who cling to a plank that is buoyant enough to support only one; the merchant who brings grain to a drought-stricken city, knowing that a plethora of grain will arrive in a following fleet; the real estate agent who advertises houses that are termite-ridden; and the starving man who can sustain himself only by taking food from another’s table….

….From the fragments left by the founders of Stoicism, Zeno and Chrysippus, the moral doctrine of the Old Stoa proposed one and only one principle, "Live according to nature." The virtuous life consisted in a conformity between the rational nature of human beings and the rational nature of the universe. This conformity was attained by a single virtue, apatheia-literally, "absence of passion." The choices of a wise agent were determined not by irrational impulse but by reason alone. Such apatheia was the sole human good: all other realities, such as illness and health, wealth and poverty, praise and ignominy, beauty and ugliness, strength and weakness, were considered external to rational nature and so were labeled "indifferent." Their value lay not in themselves but only in their use by the wise person; and the task of the wise person was not to change the world but to become a harmonious part of the cosmos….

…The Skeptic Carneades, one of the most outspoken critics of the Old Stoics, challenged the Stoic doctrine by posing cases which he claimed would expose its inner contradictions. These cases were intended to show both the unattainable nature of the morality of the Old Stoa and the paradoxical nature of all moral ideals….

…These philosophers recognized that the idealistic rigorism of the Old Stoa was intellectually paradoxical and practically inapplicable. While retaining the general outlines of the earlier doctrine they introduced further distinctions, hoping to render it more reasonable and practical. Beside kathormata, the perfect morality of the wise, was set kathekonta, the imperfect duty incumbent upon all persons. Within the category of action called "indifferent," oudetera, they introduced levels distinguishing the preferable, the rejectable, and the neutral. Preferables were those things that contributed to harmonious living and inspired desire; rejectables tended to disrupt harmonious living and inspired aversion; neutrals neither added to nor subtracted from a harmonious life. The preferables and rejectables were not, strictly speaking, "good" or "bad"; that appellation belonged only to perfect virtue. But they were advantageous or disadvantageous-that is, they had a "utility."

The task of moral deliberation was, then, to identify what was the appropriate or fitting action in any particular situation. This was identified as an action that could be supported by "reasonable justification."…

…Cicero modeled his essay On Duty on the reformed Stoicism of Panatius, but…he wove it together with the Aristotelian doctrine of virtue, stressed the problem of conflict of duties, and added some distinctively Roman examples….The terse motto of the classical Stoics, "live according to nature," was elaborated into a majestic definition of the natural law: "Right reason in conformity with nature, present in all men, unchanging, eternal, commanding all to the performance of duty, prohibiting evil." But in Cicero’s view, this noble law of nature was not by itself a sufficient guide to moral decision and action. He wrote,

"…in the performance of all these duties, we shall have to consider what is most needful in each individual case. In this way, we shall find that the fundamental moral claim of social relationship (humanitas) is not identical in every circumstance. . . .These different circumstances should be carefully scrutinized in every instance of duty, so that we may become skilled evaluators of duty and by calculation perceive where the weight of duty lies, so that we may understand how much is due to each person." (De Officiis I,59)