The applied ethical issue of euthanasia, or mercy killing, concerns whether it is morally permissible for a third party, such as a physician, to end the life of a terminally ill patient who is in intense pain.

The euthanasia controversy is part of a larger issue concerning the right to die. Staunch defenders of personal liberty argue that all of us are morally entitled to end our lives when we see fit. Thus, according to these people, suicide is in principle morally permissible. For health care workers, the issue of the right to die is most prominent when a patient in their care (1) is terminally ill, (2) is in intense pain, and (3) voluntarily chooses to end his life to escape prolonged suffering. In these cases, there are several theoretical options open to the health care worker. First, the worker can ignore the patient\'s request and care can continue as usual. Second, the worker can discontinue providing life-sustaining treatment to the patient, and thus allow him to die more quickly. This option is called passive euthanasia since it brings on death through nonintervention. Third, the health care worker can provide the patient with the means of taking his own life, such as a lethal dose of a drug. This practice is called assisted suicide, since it is the patient, and not technically the health care worker, who administers the drug. Finally, the health care worker can take active measures to end the patient\'s life, such as by directly administering a lethal dose of a drug. This practice is called active euthanasia since the health care worker\'s action is the direct cause of the patient\'s death. Active euthanasia is the most controversial of the four options and is currently illegal in the United States. However, several rights to die organizations are lobbying for the laws against active euthanasia to change.

Two additional concepts are relevant to the discussion of euthanasia. First, voluntary euthanasia refers to mercy killing that takes place with the explicit and voluntary consent of the patient, either verbally or in a written document such as a living will. Second, nonvoluntary euthanasia refers to the mercy killing of a patient who is unconscious, comatose, or otherwise unable to explicitly make his intentions known. In these cases it is often family members who make the request. It is important not to confuse nonvoluntary mercy killing with involuntary mercy killing. The latter would be done against the wishes of the patient and would clearly count as murder.

Like the moral issues surrounding suicide, the problem of euthanasia has a long history of philosophical discussion. On the whole, ancient Greek thinkers seem to have favored euthanasia, even though they opposed suicide. An exception is Hippocrates (460-370 BCE), the ancient Greek physician, who in his famous oath states that "I will not prescribe a deadly drug to please someone, nor give advice that may cause his death." The entire oath is presented below, which places emphasis on the value of preserving life and in putting the good of patients above the private interests of physicians. These two aspects of the oath make it an important creed for many heath care workers today. In medieval times, Christian, Jewish, and Muslim philosophers opposed active euthanasia, although the Christian Church has always accepted passive euthanasia.

During the Renaissance, English humanist Thomas More (1478-1535) defended Euthanasia in book Utopia (1516). More describes in idealic terms the function of hospitals. Hospital workers watch after patients with tender care and do everything in their power to cure ills. However, when a patient has a torturous and incurable illness, the patient has the option to die, either through starvation or opium. In New Atlantis (1627), British philosopher Francis Bacon (1561-1626) writes that physicians are "not only to restore the health, but to mitigate pain and dolours; and not only when such mitigation may conduce to recovery, but when it may serve to make a fair and easy passage."

Types of Euthanasia
Apart from the above classifications three types of euthanasia may be identified, depending upon the sentience of the individual.

Voluntary euthanasia
This is the truest and fullest form of euthanasia wherein the individual requests euthanasia - either during illness or before, if complete incapacitation is expected (coma would be an example).