 John Stuart Mill’s On Liberty (1859) marks the transition to a modern conception of toleration, one that is no longer occupied with the question of religious harmony and does not restrict the issue of toleration to religious differences. In Mill’s eyes, in modern society toleration is also required to cope with other forms of irreconcilable cultural, social and political plurality. Mill offers three main arguments for toleration. According to his “harm principle,” the exercise of political or social power is only legitimate if necessary to prevent serious harm done to one person by another, not to enforce some idea of the good in a paternalistic manner. Toleration towards opinions is justified by the utilitarian consideration that not just true, but also false opinions lead to productive social learning processes. Finally, toleration towards unusual “experiments of living” is justified in a romantic way (following Wilhelm von Humboldt), stressing the values of individuality and originality.