[...] At the Sorbonne, my professors systematically ignored Hegel and Marx; in a big book on the progress of conscience in the western world, Brunschvig had devoted a bare three pages to Marx, whom he placed on the same level as one of the obscurest reactionary thinkers. He was teaching us about the history of scientific thought, but no one was teaching us about the adventure of humanity. The incomprehensible uproar going on in the world might be of interest to specialists; it was not worthy of the philosopher’s attention, for, when he had got to the point where he knew that he knew nothing and that there was nothing worth knowing, he knew everything. That is why I was able to write in January: ‘I know everything; I’ve gone all the rounds.’ The subjective idealism to which I was now giving my allegiance deprived the world of its solidity and originality: it is hardly surprising that even in my imagination I could find nothing to hold on to.