One of the first utilitarian theorisers, Jeremy Bentham, is famously credited for being the founder of the doctrine. Bentham defined utility as “instrumental to happiness”. He believes that all judgements of good and bad can be based on pleasure and pain. He is seen as an advocate of psychological hedonism. In his famous introduction of An Introduction to the Principles of Morals and Legislation (1979), Bentham states “Nature has placed man under the governance of two sovereign masters, pain and pleasure.” Therefore, pain and pleasure provide the basis for his moral theory of ‘what we ought to do’. Initially, he began his career by studying law and then moved on to moral ethics in order to advise legislators. He was primarily interested in improving the law and his goal for the legislator was the utilitarian principle or the greatest happiness principle. Therefore, his advice was not initially aimed for individuals and their life choices but for the legislator. Although Bentham sees pleasure as the key of explaining how human beings act, he relies more often on the concept of pain when constructing his legal theory. While he does endorse act-utilitarianism, his ‘sanction-based’ theory of obligation is more applicable to the legal system he was so interested in improving.John Stuart Mill is also one of the most well-known utilitarian thinkers and defenders of the theory. His celebrated thoughts can be found in his famous essay: Utilitarianism. Mill observes something of a crisis in moral thinking. Philosophical thinkers have been unable to come to a consensus on the principle of what constitutes right and wrong. Mill argues that having such a foundation is necessary to legitimise morality. This is why the theory of utilitarianism is so important.