Question

What is the principle of double effect? How do these principles apply to killing in self-defense?

Answer 1

The doctrine (or principle) of double effect is often invoked to explain the permissibility of an action that causes a serious harm, such as the death of a human being, as a side effect of promoting some good end. According to the principle of double effect, sometimes it is permissible to cause a harm as a side effect (or “double effect”) of bringing about a good result even though it would not be permissible to cause such a harm as a means to bringing about the same good end. A person may licitly perform an action that he foresees will produce a good effect and a bad effect provided that four conditions are verified at one and the same time:

1. The action must be itself morally good or at least neutral: the action cannot be intrinsically evil.
2. The good result must flow from the action, not from the evil result; the evil result cannot directly produce the good result.
3. The evil outcome cannot be intended, although it is an anticipated outcome.
4. There must be a proportionate good result to permit the evil result.

So how do these principles apply to killing in self-defense?
The very act of killing someone to defend yourself from being killed begs the analyst for a careful nuance of meaning. Is not killing someone intrinsically evil? Perhaps it is, but in killing someone who is, in your view, trying to kill you, you are not killing an innocent person. Further, you could argue that you only intended to stop the attacker from killing you, not necessarily to kill him. The death of the attacker was, in that sense, an indirect and unintended outcome. Furthermore, the attacker’s death was not necessary to preserve your life; it was necessary only to intercept the attacker and disable his ability to kill you. If you intended the death of the attacker, the balance of this analysis would change. So, criteria 1, 2, and 3 of double effect may be met by careful construction of the facts. Finally, you would easily argue that criterion 4 is met since most of us would assert that the death of the attacker, though unintended and regrettable, would be tolerable because of the proportionate preservation of our own life.