The Collaborative International Dictionary of English v.0.48:

Benthamism \Ben"tham*ism\, n.
   That phase of the doctrine of utilitarianism taught by Jeremy
   Bentham; the doctrine that the morality of actions is
   estimated and determined by their utility; also, the theory
   that the sensibility to pleasure and the recoil from pain are
   the only motives which influence human desires and actions,
   and that these are the sufficient explanation of ethical and
   jural conceptions.
   [1913 Webster]