The charge that liberalism undermines itself is a familiar one. Robert Frost's famous quip captures the thought: “A liberal is a man too broadminded to take his own side in a quarrel.” Since liberalism is committed to toleration, the threat is persistent and real: how can liberals claim to tolerate diverse ethical beliefs while at the same time affirm their own principles? The matter is complex, but liberal theory can and must distinguish between the kinds of diversity that are to be tolerated and those that are not. Political liberalism takes a first step toward answering this challenge by distinguishing the right (that is, matters of justice) from the good (that is, matters concerning the content of a good life). This is more than an arbitrary conceptual distinction within the realm of the ethical. It is based on political liberalism's substantive commitment that while a broad range of doctrines of the good life are to be tolerated, its own principles of justice are correct. Furthermore, unlike other components of a comprehensive ethical doctrine, for liberals the basic principles of social justice may be coercively enforced through state power if necessary. For Rawls, following Weber, “political power is always coercive power backed by the government's use of sanctions, for government alone has the authority to use force in upholding its laws” (Rawls, 1996, p. 136. See also Rawls, 1999b, p. 207).