"On Liberty" is a political philosophy book written by British philosopher John Stuart Mill, first published in 1859. The book is one of the most influential works in the history of liberalism, and argues for the importance of individual liberty and freedom of thought and expression.
Mill argues that individuals should be free to think, speak, and act as they wish, as long as their actions do not harm others. He believes that free speech and the exchange of ideas are essential for the progress of society, and that government interference in these matters is harmful and unnecessary.
In "On Liberty", Mill also discusses the limits of individual freedom, arguing that individuals should be prevented from harming others or infringing upon their rights. He also recognizes the importance of social cohesion and collective action in certain situations, but maintains that these should be voluntary and not imposed by the government.
Overall, "On Liberty" is a powerful defense of individual liberty and a critique of the tendency of governments to interfere in the lives of their citizens. The book continues to be widely read and studied, and remains an important work in the field of political philosophy.