The ethical principle of Double Effect is used to justify medical treatment designed to relieve suffering where death is its unintended (though foreseen) consequence. According to this principle, effects that would be morally wrong if caused intentionally are permissible if foreseen but unintended. This principle is often cited to explain why certain forms of care at the end of life that result in death are morally permissible and others are not.


The ethical principle of Double Effect is used to justify medical treatment designed to relieve suffering where death is its unintended (though foreseen) consequence. According to this principle, effects that would be morally wrong if caused intentionally are permissible if foreseen but unintended. This principle is often cited to explain why certain forms of care at the end of life that result in death are morally permissible and others are not.

According to the rule, administering high-dose opioids to treat a terminally ill patient’s pain may be acceptable even if the medication causes the patient’s death. In contrast, the rule does not authorize practices such as physician-assisted suicide, voluntary euthanasia, and certain instances of forgoing life-sustaining treatment.

The principle of Double Effect comes from “the rule of double effect” developed by Roman Catholic moral theologians in the Middle Ages as a response to situations requiring actions in which it is impossible to avoid all harmful consequences. The rule makes the “intention” of the doctor a crucial factor in judging the moral correctness of the action. This is because Roman Catholic teaching has been that it is never permissible to “intend” the death of an “innocent person”. An innocent person is one who has not forfeited the right to life by the way he or she behaves, eg, by threatening or taking the lives of others.

See
“Double Effect” Fact Sheet (Adapted from SAVES — South Australian Voluntary Euthanasia Society)
Timothy Quill on the Rule of Double Effect