John Stuart Mill: Utilitarianism

What is wrong and what is right? The question philosophers have pondered throughout time has created various amount of ethical theories that argue to hold the answer to that question. One of those theories is Utilitarianism, the greatest happiness principle, which claims that actions are right as they create happiness and wrong as they create the reverse of it.   

John Stuart Mill was raised by his father to be a believer of this theory. Following the footsteps of Bentham, John Stuart Mill proposed that the foundation of ethics should be build upon the idea of Utilitarianism. This led him to publish three essays that were made to defend and to clarify the principle. Eventually those essays were put together and published in the format of a book in 1863 and those essays have developed to be essential parts of the 19th century philosophy. In this work, Mill defends the principle, answers to its critics, clarifies the principle and also adds his own to it, as he distances himself from act utilitarianism in favor of rule utilitarianism. How did Mill defend the principle and most importantly, is he right? Should ethics be grounded upon the idea of utilitarianism?   

"By happiness, is intended pleasure, and the absence of pain; by unhappiness, pain, and the privation of pleasure."