Full Idea
The strength of the doctrine of double effect seems to lie in the distinction it makes between what we do (equated with direct intention) and what we allow (thought of as obliquely intended).
Gist of Idea
Double effect seems to rely on a distinction between what we do and what we allow
Source
Philippa Foot (Abortion and the Doctrine of Double Effect [1967], p.25)
Book Reference
Foot,Philippa: 'Virtues and Vices' [Blackwell 1981], p.25
A Reaction
She objects (nicely), saying her trolley driver 'does' the side-effect killing, and someone might 'allow' an obvious criminal death. There is also an intermediate class of 'brought about', where you set up a killing, but don't do it.