My attempt to approach this topic did not come off as smoothly or cleanly as I would have hoped, so I would ask the reader to forgive the imperfections in the flow of the prose that follows.
I've often wondered why anyone bothers with utilitarianism; this wonder deepens every time I see works of modern social scientists, who seem need to constantly appeal to utilitarianism when articulating their theoretical foundations. As I considered this, it seemed to me that understanding the real meaning of utilitarianism requires us to refocus on the utilis in utilitarian. Utilis is of course the Latin word for "useful;" the utilitarians adopted this word as the name for their ethics because they viewed as good those things that were useful for accomplishing the highest good, which was the greatest possible happiness for the greatest possible number (I am here referring to classical utilitarian thinkers; we will have the opportunity to consider their modern descendants in the future). For reasons I will now lay out, I believe it would be more appropriate for us to translate the utilis in utilitarian as a statement that utilitarianism itself is a tool, and that its utility consists precisely in its capacity to allow men to leave behind theoretical questions of right and wrong and focus on "practical" concerns of actually doing ethical actions.
Utilitarianism accomplishes this transformation in the essence of ethics by reordering man's end in light of the collective maximization of pleasure and minimization of pain. It is decidedly unoriginal in doing this (the sophists had proposed precisely this sort of ethics thousands of years prior). Its originality consists in the technologization of this transformation. The sophists had only the tattered rags they stole from the cloak of dialectic to clothe their own reflections, but the utilitarians had something both greater and lesser on their side, which was the commonplace dominance of the form of the physical sciences as the preeminent mode of discourse. The "felicific calculus" of Bentham is precisely this sort of construction; a complicated mathematical shell in which a simple (and false) idea has been encapsulated.
Once this piece of technology was developed, its utility became immediately apparent. All sorts of social sciences, from psychology and sociology to political science and economics, now had a new and firm basis upon which they could conduct their inquiries. Questions about the nature or purpose of man no longer stood in the way of these fields, since a convenient answer had been found. Psychology's transformation into "pop psychology," wherein it became completely engaged in the task of providing us with the tools by which we could feel better, has its root in the utilitarian transformation of ethics. Economics could now make the assumption that the rational human being was the one who sought to maximize his own pleasure, a description which philosophy would traditionally have looked upon as quite a questionable premise indeed.
The transformation of ethics into utilitarianism is a decisive one that lies at the foundation of our age. Those of us who are concerned with moving past (the choice of this word is not accidental) modernity would do well to ponder what is transpiring in utilitarianism. As a brief closing comment that anticipates what will come later, I would like to suggest that the fatal defect of utilitarianism is that it does not actually account for the purpose of human existence, which is precisely what people (justly or unjustly) generally expect philosophers to do. The utilitarian (without appeal to other outside principles) could never explain why people should order their lives towards the pursuit of pleasure. Their counter-argument (that most people do in fact try and do this most of the time) is no counter at all, since the fact that it is generally done is hardly an argument in its favor. The utilitarians popular in our own day seem to have recognized this fact and have turned what was originally an eminently commonsense sort of thinking into an outlandishly monstrous recognition of the complete meaninglessness of human existence that follows naturally from the utilitarian premise.