As has been said, you can never do good by doing evil. That is not morally permissible – the ends do not justify the means. Commonly put, the road to hell is paved with good intentions. As has also been said, you cannot murder someone because they’re going to murder you at some indefinite point in the future. Preemptive killing is not morally permissible.
And yet…you can morally kill someone in self defense.
How is this? This is the case if the self-defense is proportionate to the threat. You cannot morally kill a man who pushes you, even though you would be acting in self defense. You cannot morally kill a man who is coming at you with a knife if you can simply shut and lock the door in between you and run away (and there’s plenty of time to do so). It is only when you are acting exclusively intending to
save your own life that you might be justified in taking the life of another.
Again, how is this? This is so because of “double effect”. There are two effects which are present: (1) saving your own life and (2) slaying the aggressor. What you intend to do is save your own life, which is morally permissible. If this may only be accomplished by killing the gun-wielding mad man, that is the least harmful means of accomplishing (1). (2) is not the intended effect, and therefore it is a second, unintended effect for which you are not morally culpable.
In the abortion context, this would play out in cases of (among a few other rare instances) ectopic pregnancies. This is where the embryo implants in the fallopian tube rather than the uterus. If the embryo is allowed to grow, the fallopian tube will rupture and the mother will die. Can you now morally kill the embryo by directly aborting it? No. Why not? Because you’re directly attacking the human being (embryo) when there’s an alternate surgical means available to correct the situation without having to directly kill the human. How? You remove the fallopian tube. It is true that the embryo will die if this is done, but that is not the intended effect. The intended effect is to save the life of the mother, and no other life is
directly attacked in this procedure (therefore the minimum level of harmful conduct is undertaken). This is the moral equivalent of closing the door on the knife wielding adversary in the example above.
What happens to the knife wielding adversary on the other side of the door? Your intention is not to kill him, so it’s not relevant for this moral analysis (unless you’re a utilitarian, and then the means never matter…only the ends…which is partly why utilitarianism is morally bankrupt).
Does that make sense?
God Bless,
RyanL
P.S.,
Aquinas on
same.