First, thanks to this author for this article.

To my mind, the most important problem of knowledge is knowledge of justice/injustice. Heretofore, 'justice' has been a matter of some belief/metaphysics/a priori/transcendental something-or-other. It would be helpful if we could have knowledge of justice/injustice that is as certain as, say, E = Mc(c).

I am convinced that such knowledge is possible: an ethic of justice that follows from observation within material existence. That observation is this [from Warren J. Samuels]: human beings have no choice but to effect choices (i.e., choose among perceived alternatives and take action to bring that choice to fruition). That observation is valid for all individuals and for all formally organized groups of people, as in societies/nations.

So the ethic of justice is mutual respect in effecting choices: taking one another into account as we effect choices. That is the definitive, sufficient, prescriptive condition of justice. The minimum, necessary, proscriptive condition of justice boils down to a handful of absolute prohibitions: no killing, harming, coercing, stealing, or manipulating (lying, cheating, etc.) to get what we want.

Since both the determiners and the referents of justice are confined to material existence, going 'outside' or 'beyond' material existence to 'invalidate' that ethic or deny its applicability to all individuals/groups of human beings is legitimately de-legitimated.