Ethical theories deal with the question of how human beings ought to behave in relation to one another. In the broadest sense, they define what qualifies as right and wrong, as well as how to promote human flourishing. There is not, however, a general consensus on what human flourishing is or how best to achieve it. The three major types of ethical theories -- deontological, utilitarian and virtue ethics -- answer these questions differently and each generates different pros and cons.
Deontological theories, or duty-based theories, hold that human beings have a moral obligation to follow certain principles. A famous example, Immanuel Kant's categorical imperative, requires that human beings treat others as ends and never as means. These types of theories tend to set out specific rules that allow people to evaluate their behaviours, which is the major advantage. Deontological theories also permit people to act above and beyond the base requirement of the rules.
Deontological theories generate several pitfalls. They do not always clarify how to rank duties, which can create insoluble dilemmas. In some cases, following a duty can lead to dangerous or disastrous outcomes. For example, a duty to tell the truth would require someone to tell a murderer where to find an intended victim. No set of rules can account for every possibility, which leaves individuals without guidance in some moral decisions.
Utilitarian theories, as espoused by John Stuart Mill, call for generating the greatest aggregate good for the greatest number of people. One major benefit of such theories is that they take consequences into account. They seek specifically to promote the human good as a whole. They also provide guidance for behaviour, enabling people to know what qualifies as the moral choice.
Utilitarian theories suffer from the problem of making it morally permissible to imprison, murder and torture individuals, even innocent ones, in order to achieve a greater good. Only total human good or happiness matters under utilitarian theories, while individual happiness or good finds consideration only as part of the total, which runs counter to many democratic ideals, such as autonomy.
Virtue Ethics Pros
Virtue ethics originates with Aristotle, who held that being ethical involves internalising a set of virtues, such as justice and bravery. These virtues then find expression through behaviour. Under virtue ethics, intentions to act ethically matter. Virtue ethics concerns itself not only with how someone acts, but with what kind of person an individual should strive to embody.
Virtue Ethics Cons
Virtue ethics cannot generate specific rules to guide behaviour. The absence of such rules makes it difficult for a group of people to come to a consensus about what constitutes ethical behaviour in a situation. Without making one virtue the supreme virtue, serious conflicts can arise about which virtue should take precedence in making choices.