Good and Evil

[Neo-Scholastic]

If the wise choice were to consist in behaving according to one's own nature, then it is still incomprehensible why the survival of a human being should matter more than the self-replication of a virus.

If your point is that human life only has value to humans, then it is a trivial one. Questions about ethics only apply to creatures endowed with reason and the capacity to freely act upon their thoughts.

So as to really annoy believers in truth, I would also like to throw in a quote from Michel Foucault: "'Truth' is to be understood as a system of ordered procedures for the production, regulation, circulation and of operation of statements. 'Truth' is linked in a circular relation with systems of power which produce and sustain it, and to effects of power which it induces and which extend it. A 'regime' of truth.”

The Foucault quote makes no reference to the conformity of propositions with objective reality. So in actuality, he’s only talking about how people use diction and grammar. The quote says nothing whatsoever about knowledge.

Adam LOV introduced the question of whether essences are real in any meaningful sense…one can point to the sociological essentialism holding that traits like race, ethnicity, and gender are immutable. This essentialism was cited to help support colonialism and racial apartheid policies no longer considered ethical. We now hold that race, ethnicity, and gender are all social constructs.

You are correct to say that race, ethnicity and gender are social constructs. It does not follow from that fact that there is no such thing as human nature. The theory of evolution was used to justify eugenics, genocide, and social Darwinism. Those misapplications of the theory did not invalidate the theory of evolution.

…the fact that ethics evolve over time shows that whatever's "inside" situations of right and wrong isn't immutable, that is, it isn't a pure essence like "triangleness" is for triangles.

Scientific understanding also has evolved over time. People today have a much more accurate and precise understanding of objective reality than their predecessors. Just because it is easier to understand the nature of triangles (or electrons) doesn’t mean that something as complex as a human being doesn’t have an essential nature. It just takes more effort and discernment to uncover it. Understanding human nature will always be a work in progress, but if you abstract away all the accidental properties of something what remains are the essential properties without which a particular would cease to partake of the universal. With respect to people, the things that differentiate one human from the next, like skin color and sex, are accidental features. The common features shared by all humans are essential features, like rationality. The objectivity of moral judgment depends on keeping these distinct.