One of the most important and widely-held moral beliefs in the modern world is a belief in the principle of equal liberty. According to this principle individuals should have the maximum freedom that is compatible with an equal freedom for all other individuals. Ever since the Enlightenment the principle of equal liberty has provided a basic moral reference point against which the legitimacy of social and political institutions has been judged. And it is, I think, indisputable that this continues to be true today.