overacute

He wants us to recognize, first, that he suffers from overacute senses and, second, that the vulture eye of the old man, not hatred or greed (rather trite, uninteresting, normal motives), is what compelled him to commit his atrocity (here is also expeditio, if we can accept the term as meaning not just the rejection of all but one of various reasons why something should be done but also of why something was done).

Argument #1: I am not mad but suffer from overacute senses, especially of the auditory capacity ("And have I not told you that what you mistake for madness is but over acuteness of the senses?" [5: 91]).