salvation for a man to omit the act of moderate defence in order to
avoid the killing of another; because man is more bound to take
thought for his own life than for the life of his neighbour. But
because to kill a man is not allowable except by act of public
authority for the common good, it is unlawful for a man to intend
[that is, elect and choose as a means] to kill another man in order to
defend himself, unless he be one who has public authority, who
intending [electing] to kill a man in order to his own defence, refers
this to the public good."

2. The right then of self-defence even to the shedding of blood
involves a mere exercise of indirect killing for a proportionably
grave cause. The cause in question is the defence of your own life, or
your friend's, or of some other good or possession that can weigh with
life, as the honour and inviolability of your person, or a large sum
of money. This must be in present danger of being taken away otherwise
than in due course of justice. The danger must be present, and even
imminent, not prospective. The right of self-defence even to the
grievous harming of the aggressor, endures only while the danger from
him is imminent, not when it is past, or the evil is already done. The
right supposes no moral obliquity, no formal injustice on the part of
the aggressor: he may be a madman making for you with a drawn sword.
Nay further, not even _material_ injustice--that is, the quality of an
act which would be _formally_ unjust, if only the agent knew what he
was about--is required. All that is requisite is that your life, or
something equivalent to life, be threatened, _not in due course of
law_.

3. The essential idea of self-defence is that of stopping a
trespasser, one who, however innocently, is going about to trench on