To ‘plume up the will,’ to heighten the sense of power or superiority—­this seems to be the unconscious motive of many acts of cruelty which evidently do not spring chiefly from ill-will, and which therefore puzzle and sometimes horrify us most.  It is often this that makes a man bully the wife or children of whom he is fond.  The boy who torments another boy, as we say, ‘for no reason,’ or who without any hatred for frogs tortures a frog, is pleased with his victim’s pain, not from any disinterested love of evil or pleasure in pain, but mainly because this pain is the unmistakable proof of his own power over his victim.  So it is with Iago.  His thwarted sense of superiority wants satisfaction.  What fuller satisfaction could it find than the consciousness that he is the master of the General who has undervalued him and of the rival who has been preferred to him; that these worthy people, who are so successful and popular and stupid, are mere puppets in his hands, but living puppets, who at the motion of his finger must contort themselves in agony, while all the time they believe that he is their one true friend and comforter?  It must have been an ecstasy of bliss to him.  And this, granted a most abnormal deadness of human feeling, is, however horrible, perfectly intelligible.  There is no mystery in the psychology of Iago; the mystery lies in a further question, which the drama has not to answer, the question why such a being should exist.

Iago’s longing to satisfy the sense of power is, I think, the strongest of the forces that drive him on.  But there are two others to be noticed.  One is the pleasure in an action very difficult and perilous and, therefore, intensely exciting.  This action sets all his powers on the strain.  He feels the delight of one who executes successfully a feat thoroughly congenial to his special aptitude, and only just within his compass; and, as he is fearless by nature, the fact that a single slip will cost him his life only increases his pleasure.  His exhilaration breaks out in the ghastly words with which he greets the sunrise after the night of the drunken tumult which has led to Cassio’s disgrace:  ’By the mass, ‘tis morning.  Pleasure and action make the hours seem short.’  Here, however, the joy in exciting action is quickened by other feelings.  It appears more simply elsewhere in such a way as to suggest that nothing but such actions gave him happiness, and that his happiness was greater if the action was destructive as well as exciting.  We find it, for instance, in his gleeful cry to Roderigo, who proposes to shout to Brabantio in order to wake him and tell him of his daughter’s flight: 

     Do, with like timorous[116] accent and dire yell
     As when, by night and negligence, the fire
     Is spied in populous cities.

All through that scene; again, in the scene where Cassio is attacked and Roderigo murdered; everywhere where Iago is in physical action, we catch this sound of almost feverish enjoyment.  His blood, usually so cold and slow, is racing through his veins.