As Dr. Curtis Brown, professor of philosophy at Trinity University, explains, the existence of moral preferences provides a basic defense for the existence of moral principles. If a person has two possible choices, A and B, and Choice A appears undeniably preferable over Choice B on a moral basis, rather than on the basis of simple, morally indifferent preference, then a reason must exist governing why Choice A claims that moral preference. On a simplified level, the choice between chocolate or vanilla ice cream has no apparent relationship to morality. In the choice between keeping a promise and breaking one, however, keeping a promise generally seems morally preferable. If an individual accepts this as true, then it stands to reason that a moral principle concerning promises exists to guide this preference.
Moral principles, in turn, provide guidelines for the development of moral preferences and moral reasoning. Dr. Don Berkich at Texas A&M University lists the Principles of Sufficient Moral Reason as well as the Principles of Moral Analogy. Sufficient moral reason essentially states that if an action is morally permissible, obligatory or impermissible, a moral reason exists that explains why that action has its morally permissible, obligatory or impermissible status, respectively. Moral analogy means that if one of any two actions, equal and similar in all morally relevant respects, has a permissible, obligatory or impermissible status, then the second has that same status.
Normative ethics determine how individuals reach moral principles that regulate right and wrong. Three normative strategies include virtue theories, duty theories and consequentialist theories. Dr. James Fieser of the University of Tennessee at Martin explains the basics of these theories. Virtue theories stress the importance of developing good habits of character, such as sincerity or courage. Duty ethics stress the importance of foundational obligations, like caring for our children or refraining from committing murder. Consequentialist theories insist that correct moral conduct depends only on a cost-benefit analysis of actions, meaning that the morally correct action is that which has the most favorable consequence.
Further complications arise when considering whether or not moral principles exist as absolute or contributory concepts. Professor Jonathan Dancy explains this complication in the Stanford Encyclopedia of Philosophy. For a moral principle to exist absolutely, that principle must hold true universally and in all circumstances. Simplistically speaking, if one must keep one's promises absolutely, then no reason can justify that action. A contributory moral principle means that, while breaking a principle may count against the morality of an action, that action may remain morally best if other moral principles count for it. If breaking a promise brings greater benefit to your friend, for example, then that action may remain morally commendable.