Any sudden alteration of our bodily appearance sensibly impedes the movement of imagination.

A patient after a fever, when he first looks in the glass, exclaims, "I don't know myself." More commonly the bodily changes which affect the consciousness of an enduring self are such as involve considerable alterations of coenaesthesis, or the mass of stable organic sensation.

Thus, the loss of a limb, by cutting off a portion of the old sensations through which the organism may be said to be immediately felt, and by introducing new and unfamiliar feelings, will distinctly give a shock to our consciousness of self.
Purely subjective changes, too, or, to speak correctly, such as are known subjectively only, will suffice to disturb the sense of personal unity.

Any great moral shock, involving something like a revolution in our recurring emotional experience, seems at the moment to rupture the bond of identity.

And even some time after, as I have already remarked, such cataclysms in our mental geology lead to the imaginative thrusting of the old personality away from the new one under the form of a "dead self."[134] We see, then, that the failure of our ordinary assurance of personal identity is due to the recognition of difference without similarity.