Aristóteles y la justicia natural

In his Nicomachean and Eudemian Ethics Aristotle says of natural justice that it is changeable and not the same everywhere. The implication seems to be that no action, not even murder, is always wrong. But, as is evident especially from his Magna Moralia, Aristotle distinguishes justice into the "what" (equality), the "in what" (proportion between persons and things), and the "about what" (what things are exchanged with which persons). He allows for variability only in the "about what". He allows for no variability in the "what" and the "in what". The fact is clear from adultery, which Aristotle says is always wrong. He says the same elsewhere of other acts, as abortion, euthanasia, and usury.