Kant

It is comprised of many components and represents different things to different people. Whether man is dedicated to becoming a millionaire, famous, or living a virtuous and healthy life, he is merely exercising contrary means to the same end -- "pleasure and freedom from pain.".
             Utilitarianism began life as an ethical principle under Jeremy Bentham who theorised that an action if right if it produces the greatest good for the greatest number of people. In its original form the argument had many flaws so John Stuart Mill decided to defend the principle of Utility against it's critics by refining it's ideas making them more practical in society. .
             Jeremy Bentham's theory of Utilitarianism was based on an observation, that the definition "good" in terms of "pleasure" and established that two things are intrinsically good namely pleasure itself and freedom from pain. His logical progression deduced that we ought to increase what is good by increasing what brings us pleasure or freedom from pain. Thus the Principle of Utility was created - "act in such a way as to bring about the greatest happiness of the greatest number working to increase the total sum of pleasure. Mill felt that he could strengthen the argument for Utilitarianism by clarifying it's points. In his famous argument he simplifies the terms "happiness" and "pleasure" used by Bentham as one major criticism is that the word "pleasure" does not have the same meaning as the word "good". He attempts to silence critics of the Epicurian substitution of words by his good but less than airtight argument. His flaws lay again in meaning of words, as desirable is used in two different ways- "can be desired" and "ought to be desired". Also he begins by stating the obvious that individuals desire their own happiness but concludes that everyone's happiness is desirable to everyone else. More correctly it should read "desirable to the individual" and then the argument cease to work.