The primary difference between deontology and utilitarianism, two competing systems of ethics, is that the former system is concerned with whether an act is intrinsically right or wrong, while the latter system believes that only the consequences of an act are important. Deontology deals with intentions and motives. Utilitarianism focuses only on results.
Advocates of utilitarianism believe that all actions must seek to produce the greatest good for the greatest number of people, according to the Stanford Encyclopedia of Philosophy. This applies even if an act harms an innocent person. For example, if a surgeon has the chance to save three lives by harvesting the organs of a healthy person, utilitarian theory suggests that harming the healthy person is acceptable to save a greater number of lives.
By contrast, deontology focuses on the moral aspects of any action, not its consequences. This philosophy believes that some acts are always wrong, regardless of the consequences. Deontologists find lying to be unacceptable, for example, even when someone lies in order to bring about a desirable result.
Both of these systems have weaknesses. For instance, critics charge that utilitarianism justifies enslaving a small group of people in order to help a larger group. Critics of deontology point out that its rigidity does not allow for exceptional cases where a morally dubious action avoids causing harm to others.