> Ethics are reached via consensus.
Absolutely not! This is cultural relativism, and frankly, it would be circular: how exactly are we converging on a consensus if not from some preexisting sense of the good?
The only defensible objective basis for the good is the nature of a thing and what actualizes the potentials determined by that nature, thus actualizing the thing as the kind of thing it is. Morality, only possible for things that have the capacity to comprehend their options for action (intellect) and choose freely among them (will) on the basis of that understanding, therefore concerns the question of whether an act performed by a thing furthers or frustrates the actualization of that thing.
By cutting off my arm for no proportionate reason, I do an immoral thing, because it is my nature to have that arm, but if I have gangrene in that arm that threatens my life, then removing the gangrene with the undesirable side effect of losing an arm is morally justifiable, even if the loss of the arm is not good per se.
Murdering a human being is gravely immoral, because it directly contradicts my nature as a social human being in a very profound and profoundly self-destructive way. However, killing a would-be murderer in defense of my life or that of another is a morally very good deed; it is in accord with my social nature, and indeed can be said to actualize it more fully in some respect.
> The rest of us derive our principles from functioning mammalian emotional circuits
Please refrain from making such silly pseudoscientific and pseudophilosophical statements.
That being said, calculation is insufficient, because such calculation is formal: it explicitly excludes the conceptual content of propositions. But concepts are the material "carriers" of comprehension of what things are. We can also analyze concepts. Now, we can say that we can calculate a formal deduction according to formal rules, but we cannot calculate a concept or its analytical products. This is the produce of abstraction from concreta. Formal systems abstract from these. They are blind to conceptual content, on purpose. And having used a formalism to derive a conclusion, we must interpret the result, that is, we must reassign concepts to symbols that stand in for them. So formal systems are useful tools, but they are tools.