John Stuart Mill 1806 -1873 was an English philosopher, political economist and member of parliament. One of the most influential thinkers in the history of western liberalism, he contributed widely to social theory, political theory and political economy. He was widely acknowledge to promote the thought, that government (formal institutions) must have some limits to intervene in individuals liberty. He coined the term legitimate government intervention. He started this debate that in self-regarding actions, govt. should not intervene because this is against individual liberty, for instance, alcohol consumption. Government is only allowed to intervene in other-regarding actions, for example driving after consuming alcohol. He declared that Govt is not justified to intervene in those matters which create harm for a person by himself like alcohol consumption in bedroom or bar. To, legitimize his theory of liberty, he formulated a very strong ethical theory Utilitarianism, which gives a new wider and liberal principle to distinguish between right and wrong. The core of ethics is ‘how to distinguish between right and wrong. Mill put forward a new ethical theory while Divine command theory, Kantianism and Aristotelian ethics are already prevailing. According to his Utilitarianism philosophy ‘every action is right if it brings no harm to other’ his philosophical narrative states that, good action is that which brings greatest good for greatest number of people. Therefore, he promoted the idea of liberty further by saying it the greatest good that benefits the greatest number of people. He philosophy promoted liberty in all domains of personal life. He was the first to promote feminist right in parliament of UK and raised voice for subjection of women and right to vote. He said, women should be free, enjoying as much as liberty as men do. J. S. Mill was inspired by Adam Smith, free market idea for efficiency, he brought his philosophy to sociological side. By saying, the height of human civilization – French revolution, as a bi-product of liberty, therefore, for further progress of human civilization, more liberty should be awarded to common masses by the govt, and the starting point should be women, which is most vulnerable in terms of liberty. His writings were so influential, that Utilitarianism has influenced nearly all aspect of govt laws that deal with sociology. New law making under his influence, gave more liberty to society, starting from women. This changed the norms and in-formal institutions of west.