Ethical dilemmas, also known as moral dilemmas, have been a problem for ethical theorists as far back as Plato. An ethical dilemma is a situation wherein moral precepts or ethical obligations conflict in such a way that any possible resolution to the dilemma is morally intolerable. In other words, an ethical dilemma is any situation in which guiding moral principles cannot determine which course of action is right or wrong.
One well-known and frequently discussed example of an ethical dilemma was offered by Jean-Paul Sartre. Sartre asks us to imagine a young man who lives with his mother; he is her only happiness in life. But the young man lives in occupied France during World War II and feels obliged to fight in the war. What does the young man do? Another dilemma is a situation in which three family members are being held captive. The captives give one the choice of which of the other two will die. If there is no choice, they all will be killed.
Some moral dilemmas are the result of uncertainty about the kind of actions one should take to achieve the best outcome. This can be because the future results of each decision are unknowable or because facts that can influence certain outcomes are not available. For example, if Sartre's young man knew he would help turn the war effort around and that he would survive it to return to his mother, he'd be better equipped to make a decision. But he cannot know this, so his situation remains uncertain.
Sartre's young man is the result of a self-imposed dilemma; he projects two obligations upon himself that cannot be reconciled. Self-imposed moral dilemmas are the result of two actions one feels one must take that cannot be reconciled with each other.
World-imposed ethical dilemmas are of the type described in the second example, where a family member must choose which of two other members must die. He is not instigating the decision; it is being forced upon him from the outside, and he is bound by it to make a decision.
Ultimately, ethical dilemmas require choices, and merely refraining from action can be a moral decision. In some moral dilemmas, one must choose whether to disobey a particular prohibition, such as a law, when compliance results in immoral consequences. In this case, inaction is obeying the law, but the result is morally reprehensible.