I agree with where you ended: in that century advances in technology took to new depths the impulse that has always been with human beings to divide into ‘us’ and ‘them’ and to attack one another on that basis. (You did leave out Nationalism, which caused and sustained WWI.)

All of that takes place in the plane of beliefs, however, not rationality. As I say every chance I get, ideologies are secular religions. Ideologies are based on beliefs as surely as theologies are, and are therefore no more rationalistic than spiritual religions are.

Beliefs divide people. They always have. They always will.

We have always thought of justice as an aspect of morality, and moralities are always based on beliefs. My studies have taught me that justice can in fact only be found in rationality. Our rational capacity is the only possible source for the commonality that justice requires.

The ethic of ‘real justice’ follows from the simple observation that human beings have no choice but to effect choices (i.e. choose among perceived alternatives and take action to bring that choice to fruition) [which I got from Warren J. Samuels]. To act justly is to recognize fellow humans as fellow humans by respecting the capacity all people have to choose for themselves.

That might seem like a thin reed on which to build something as big and strong as justice must be. It is in reality, however, the very thing we need to finally overcome, at long last, the murderous insanity of ‘us’ versus ‘them’.