The immune system embodies a simple binary distinction: self or other. When other appears where self should be, action is taken. We dramatize this with our talk of pathogens, antibodies, attack and counterattack, infection, and the like, but of course such epithets only make sense from the point of view of the immune system. Pathogens are not ethically challenged entities, and antibodies are not little determined Terminators.
As we understand ourselves better, we may find ourselves making a similar distinction. For now, the issue of what “we” are seems to be undiscussed, leaving it in an odd schizophrenic state of both Mind and Body. But our discourse is improving, and as we learn more, so the “we” that we identify with will necessarily change. This is a good thing, as the only way to face the large questions of planetary husbandry will require us to be plastic and capable of learning here.