"And yet it is clear that the normal development of a human being implies an increasingly precise and, as it were, automatic division between what concerns him and what does not, between things for which he is responsible and those for which he is not. Each one of us becomes the centre of a sort of mental space arranged in concentric zones of decreasing interest and participat ion. It is as though each one of us secreted a kind of shell which gradually hardened and imprisoned him; and this sclerosis is bound up with the hardening of the categories in accordance with which we conceive and evaluate the world."