On Liberty; Theory of liberty is a work by John Stuart Mill, a British philosopher, sociologist, economist and politician.

Although this book is not large, more like a tract, it became a fundamental basis for the liberalism theory. With a whole heart, it defends the freedom of speech and protests against the censorship. It critisizes the wickednesses of the bourgeois regime (the property unequality, cult of money and low life level of the working class). To overcome that the author offers to use the principles of social reforms.