Author, Simon.
Published, April 29, 2009.

The conditions of the Doctrine of Double Effect are as follows:

1. The agent acts with good intention, and attempts to bring about a good effect.
2. The agent does not want to bring about the predicted negative consequences and attempts to avoid or mitigate them as much as possible.
3. The agent treats the negative consequences neither as the end, nor as the means to another end.
4. There is acceptable proportionality between the negative consequences and the positive effects. 

Another example in which this could be applied might be that a strategic bomber bombs a munitions factory in order that its production will be either reduced or stopped. In doing so, the bomber knows innocent civilians may be killed. The strategic bomber satisfies condition 1 – he acts with good intention to bring about a good effect. He wants to destroy an enemy munitions factory’s capacity to produce weapons and support the enemy’s war effort. The bomber satisfies condition 2 – he does not want to bring about the foreseen negative consequence of the civilian deaths. He will try to bomb as accurately as he can, in order to limit the consequences. The bomber also satisfies condition 3 – the death of the innocent civilians is neither the means nor the end of his attack. It is questionable, though, as to whether he satisfies condition 4 – proportionality.

This is precisely where Thomas Aquinas makes his qualification; the question of proportionality. If the negative consequences are disproportionate to the positive effects, then the act is not justified. This condition is dubious, which is why it is very hard, if not impossible, to fight wars within the principle of jus in bello. It is even more dubious when combined with the principle we are most interested in, discrimination. As will now be shown, because condition 4 is found to be dubious, it makes the other conditions dubious too. This leads to an irreconcilable position.

Part 7, ‘Strategic Bomber or Terror Bomber?’, is here.