I’m keep coming across good passages from Otto Weininger’s Sex and Character. Bear with me:
On the self and others, individualism and universalism:
It is easy to give proofs. Only brutalised criminals and insane persons take absolutely no interest in their fellow men; they live as if they were alone in the world, and the presence of strangers has no effect on them. But for him who possesses a self there is a self in his neighbour, and only the man who has lost the logical and ethical centre of his being behaves to a second man as if the latter were not a man and had no personality of his own. “I” and “thou” are complementary terms. A man soonest gains consciousness of himself when he is with other men. This is why a man is prouder in the presence of other men than when he is alone, whilst it is in his hours of solitude that his self-confidence is damped. Lastly, he who destroys himself destroys at the same time the whole universe, and he who murders another commits the greatest crime because he murders himself in his victim. Absolute selfishness is, in practice, a horror, which should rather be called nihilism; if there is no “thou,” there is certainly no “I”, and that would mean there is nothing.
There is in the psychological disposition of the man of genius that which makes it impossible to use other men as a means to an end. And this is it: he who feels his own personality, feels it also in others. For him the Tat-tvam-asi is no beautiful hypothesis, but a reality. The highest individualism is the highest universalism.