Which philosopher focused on utilitarianism and individual liberties?

John Stuart Mill is the philosopher known for his contributions to the development of utilitarianism and his emphasis on individual liberties. Utilitarianism is the ethical theory that promotes actions that maximize happiness and well-being for the greatest number of people. Mill's work built upon the foundations laid by Jeremy Bentham, who initially formulated the principles of utilitarianism.

In his writings, particularly in "On Liberty," Mill argues for the protection of individual rights and freedoms, asserting that individuals should be free to pursue their own paths as long as they do not harm others. His discussions on liberty are fundamental to liberal thought, advocating for personal autonomy while balancing societal interests. Mill's perspective was crucial in shaping modern concepts of democracy and social justice, making him a key figure in both political philosophy and moral theory.

The other philosophers mentioned each had differing focuses: Karl Marx concentrated on class struggle, capitalism, and the role of economic factors in societal evolution; Friedrich Engels, a collaborator with Marx, similarly focused on historical materialism and critiques of capitalism; and Adam Smith is best known for his work on economic theory and the invisible hand, emphasizing free markets rather than explicitly discussing utilitarian ethics or individual liberties in the way Mill did.