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The principle of double effect

Updated Wednesday, 27th February 2008

Is there a difference between deliberately killing someone and doing something that will lead to their death? Nigel Warburton explores the Doctrine of Double Effect.

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Some people believe there is a significant moral difference between deliberately killing someone and performing an action that you know will result in another's death. These people subscribe to what is known as the Doctrine of Double Effect, a principle drawing a distinction between intentionally doing something undesirable and doing something where you foresee an undesirable consequence, but don’t wish this consequence. The name 'Double Effect' comes from the fact that the action in question is thought to have two effects: a good one (intended) and a bad one (merely foreseen).

It may sound esoteric, but this principle has many vitally important applications: for example in medical cases. A doctor may justify administering a lethal pain-killing drug that predictably hastens a patient's death on the grounds that she aims to lessen the patient's pain rather than kill him. 

Critics of this view, including strict utilitarians, will say that if the predictable consequences are the same, the moral worth of the actions must be the same. If you know your actions will result in a death, what difference can it make if you intend this death, rather than merely foresee it? Some of those who subscribe to the Doctrine of Double Effect do so because they are members of a religion that has an absolute prohibition on intentional killing; from outside these religions the double effect doctrine can look like a convenient kind of conscience-saving rationalization. 

Through a series of ingenious, if highly implausible, thought experiments involving out-of-control trolleys, innocent people tied to railway tracks (and, in one case, a fat man pushed over a bridge), Michael Otsuka defends the Doctrine. In this weeks’ Ethics Bites, he claims that our intuitions about these cases support the Doctrine. 

I'm not completely convinced he's right. Perhaps what we need to do is abandon our intuitions, rather than stick to the Doctrine.

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