Utilitarian ethics was formulated first by Jeremy Bentham in 1781, and later championed and elaborated by the philosopher John Stuart Mill. This ethic states that the rightness of an action entirely depends on the value of its consequences, and that the usefulness can be rationally estimated. (As opposed to, say, the intentions behind it, the social acceptability, or the historical/religious principles of ethics that might disagree.)
The value of said consequences are measured by the Greatest Happiness Principle, which states that each person's happiness counts for exactly the same as every other's, and that value of an action is positive if and only if that action increases the total happiness in the world.
The central idea of the utilitarian theory is that ethics is a reality which can be demonstrated. One can define it without religious dogma, nor external regulation, starting from the only elementary motivations of human nature -- seeking happiness or pleasure, and to escape suffering. This principle is formulated in the opening sentence of Bentham's book, Principles of Morals and Legislation (printed in 1781, but only published in 1789) :
- Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. It is for them alone to point out what we ought to do, as well as to determine what we shall do. On the one hand the standard of right and wrong, on the other the chain of causes and effects, are fastened to their throne.
