John Stuart Mill (1806-1873) was interested in the nature of Civil Liberty, and the limits to the power that a Government can legitimately exercise upon its citizens. He believed that some worrying tendencies could be observed in the England society of his time, and tried to warn others about them. In "On Liberty," Mill explains his ideas regarding the preservation of individual liberties, not only due to the fact that they are rights owed to everyone, but also because they benefit society as a whole. For example, when he says that liberty of thought and of discussion must be preserved, he tells us that "Wrong opinions and practices gradually yield to fact and argument: but fact and arguments, to produce any effect on the mind, must be brought before it". How can mistaken beliefs or actions be proven wrong, if dissent is forbidden? The loss for society is clear: "If the opinion is right, they are deprived of the opportunity of exchanging error for truth; if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error". In order to preserve the liberties included in the concept of Civil Liberty, Mill points out that there must be limits to the action of the Government. He says that "The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others". Any other reason is simply not good enough. Thus, John Stuart Mill highlights the rights of the individual, but also the limit to those rights: the well-being of others. "On Liberty" is not too long, and though the language is a bit dated, "On Liberty" was written many years ago. Notwithstanding that, this book is well-worth the effort to read it, because it is even more relevant today than when it was first published in 1859. Are individual rights important? Why? Do they have a limit? Answers to these questions, and much more, are to be found in this classic by John Stuart Mill.