The English philosopher John Locke (5 letters) was an influential Enlightenment thinker who wrote extensively on the philosophy of government and civil society. He is best known for his work 'Two Treatises of Government' which argued for the natural rights of individuals and the need for a social contract between the government and its citizens. The English philosopher John Stuart MILL (4 letters) was a 19th century utilitarian philosopher who wrote on a wide range of topics including economics, politics, and ethics. He is best known for his work 'On Liberty' which argued for individual freedom and the need for limits on the power of the state.