The key concept in On Liberty is the idea that liberty is essential to ensure subsequent progress, both of the individual and society, particularly when society becomes more important than the state. This state of affairs would be attained in a representative democracy in which the opposition between the rulers and the ruled disappears, in that the rulers only represent the interests of the ruled. Such a democracy would make the liberty of the individual possible, but it would not guarantee it. When society becomes free of the constraints of government, it begins to entrench the interests of a select and powerful few, which threatens individual liberty in a new way. Mill grapples with the problem of envisioning society progressing in such a way as to prevent the repression of the individual by the ever more powerful and confident majority. Social progress can only take place if limits are placed on individual liberty, but it also necessitates the freeing of the individual from such limits.
Mill sidesteps this dilemma by delving into moral theory, where the only important thing is the happiness of the individual, and such happiness may only be attained in a civilized society, in which people are free to engage in their own interests, with all their skills and capabilities, which they have developed and honed in a good system of education. Thus, Mill stresses the fundamental value of individuality, of personal development, both for the individual and society for future progress. For Mill, a civilized person is the one who acts on what he or she understands and who does everything in his or her power to understand. Mill holds this model out to all people, not just the specially gifted, and advocates individual initiative over social control. He asserts that things done by individuals are done better than those done by governments. Moreover, individual action advances the mental education of that individual, something that government action cannot ever do, for government action always poses a threat to liberty and must be carefully watched.