Think of Milbank’s question, Can a Gift Be Given?  Derrida says no, because the purity of the gift is always polluted by expectations of return.

Dostoevsky asks, Can a Crime Be Committed?  And he returns something like Derrida’s answer, though ironically.  Raskolnikov claims in his confession to Sonya that he “wanted to murder . . . without casuistry, to murder for my own sake, for myself alone!”  His confession is a confession of failure to do what he wants, because in the end he kept introducing “casuistry.”  He killed to help his family; he killed to right the wrongs of society; he killed to rid society of a blood-sucking little spider.  The purity of his crime is polluted by motivations, human motivations.

Raskolnikov at least cannot commit a crime, because with each impurity and each act of casuistry, he proves himself still flesh, still a member of the human race that he wanted to transcend.  In spite of himself, he finds another law warring in his members, a divine logic that his will cannot control.