Natural justice is a pledge of reciprocal benefit, to prevent one man from
harming or being harmed by another.
Those animals which are incapable of making binding agreements with one
another not to inflict nor suffer harm are without either justice or injustice; and
likewise for those peoples who either could not or would not form binding
agreements not to inflict nor suffer harm.
There never was such a thing as absolute justice, but only agreements made
in mutual dealings among men in whatever places at various times providing
against the infliction or suffering of harm.
~ Epicurus, Principal Doctrines