Elizabeth Anscombe, answered from the texts and cited to the page.
The distinction between what an agent intends and what he merely foresees as a side-effect of his action is, I argued in War and Murder, absolutely essential to Christian ethics — and not only to Christian ethics.1 The reason is this: Christianity forbids certain things as bad in themselves. But if I am answerable for the foreseen consequences of an action just as much as for the action itself, those prohibitions collapse.
If someone innocent will die unless I do a wicked thing, then on that view I am his murderer in refusing; all that is left is to weigh up evils. The principle of double effect — or, as I prefer to call its core, the Principle of Side-Effects — blocks that slide: you are no murderer if the man's death was neither your aim nor your chosen means, and if you had to act as you did or else do something absolutely forbidden.2
So stated, the principle does one specific piece of work. It tells you that an action is not excluded by the prohibition on intentional killing merely because death results from it as an unintended side-effect.3 What it does not do — and this is where confusion has accumulated — is settle what further conditions must be met before such unintended causing of death is permissible.
I came to see that the Doctrine of Double Effect as traditionally presented is not a single principle but a package, and that we should split it up.4 Once the Principle of Side-Effects is accepted, further principles are needed. One that seems both obvious and covers a good many cases is this: where the death of the victim is intrinsically certain, or very likely from the nature of the case, that alone would exclude the action — even if the death is not intended.5
Surgery performed not to kill but to harvest an organ, where death is a near-certain consequence of the operation itself, would be murderous on this ground even though killing was not the aim.6 The doctrine has also been systematically abused, and I think the abuse has a clear historical source. From the seventeenth century onwards, Cartesian psychology treated intention as an interior act of the mind producible at will.
If intention is what determines the goodness or badness of an action — as it is — then on that picture a marvellous escape route opens: you need only "direct your intention" in a suitable way, make a little speech to yourself beginning "What I mean to be doing is...," and any action becomes lawful.7 The Holy See condemned specific instances of this perverse doctrine repeatedly, and rightly.8
A devout Catholic bomber, on this logic, secures by a direction of intention that any shedding of innocent blood is "accidental." I know of a Catholic boy puzzled at being told by his schoolmaster that it was an accident that the people of Hiroshima and Nagasaki were there to be killed — and however absurd it sounds, such thoughts have been common.9
The remedy is to be clear about what intention actually is. It is nonsense to pretend that you do not intend what is the means you take to your chosen end.10 Where the crushing of a man's head is the immediate effect of moving a rock, and you know this, you cannot pretend not to intend it if you are willing to move the rock.11 The room for saying you did not intend a result arises only where the result is not so immediate — where the rock must take a further path before causing death, and there is genuine space between your action and the outcome.12
Without that clarity, the principle of double effect licenses everything and prohibits nothing; the absolute prohibitions of Christian ethics go to pieces, and anything can be and is justified.13
The distinction between the intended, and the merely foreseen, effects of a voluntary action is indeed absolutely essential to Christian ethics.Part One: Ethics, pp. 69–70
No, you are no murderer, if the man's death was neither your aim nor your chosen means, and if you had to act in the way that led to it or else do something absolutely forbidden.Part One: Ethics, pp. 69–70
the principle of side-effects says no more than that moving the rock is not excluded by the prohibition on intentional killing.Human Life, Action and Ethics, pp. 213–214
I have come to realise that the Doctrine of Double Effect comprises several things, merely including this 'principle of side-effects', and that we should split it up.Human Life, Action and Ethics, pp. 213–214
The intrinsic certainty of the death of the victim, or its great likelihood from the nature of the case, would exclude moving the rock. Here is a reasonable principle.Human Life, Action and Ethics, pp. 214–215
Surgery would be thought murderous, even though it was not done in order to kill, but, say, to get an organ for someone else, if the death of the subject were expected as a near consequence, pretty certain from the nature of the operation.Human Life, Action and Ethics, pp. 214–215
an intention was an interior act of the mind which could be produced at will. Now if intention is all important —as it is— in determining the goodness or badness of an action, then, on this theory of what intention is, a marvellous way offered itself of making any action lawful. You only had to 'direct your intention' in a suitable way.Part One: Ethics, p. 70
This perverse doctrine has occasioned repeated condemnations by the Holy See from the seventeenth century to the present day.Part One: Ethics, p. 70
The devout Catholic bomber secures by a 'direction of intention' that any shedding of innocent blood that occurs is 'accidental'. I know a Catholic boy who was puzzled at being told by his schoolmaster that it was an accident that the people of Hiroshima and Nagasaki were there to be killed.Part One: Ethics, p. 70
It is nonsense to pretend that you do not intend to do what is the means you take to your chosen end.Part One: Ethics, p. 70
if you do know, then where the crushing is immediate you cannot pretend not to intend it if you are willing to move the rock.Human Life, Action and Ethics, pp. 213–214
the rock you are moving has to take a path after your immediate moving of it, and in the path that it will take it will crush his head. Here there is indeed room for saying that you did not intend that result, even though you could foresee it.Human Life, Action and Ethics, pp. 213–214
Without understanding of this principle, anything can be — and is wont to be — justified, and the Christian teaching that in no circumstances may one commit murder, adultery, apostasy (to give a few examples) goes by the board.Part One: Ethics, pp. 69–70