 Others, notably Klosko (2005), Jonathan Wolff (1995, 2000), and Dudley Knowles (2010) have explicitly called for a pluralistic or multiple-principle approach to political obligation. There is no single answer to the problem of political obligation, as they see it, because the problem has more than one aspect. Not every “member” of a polity will stand in the same relation to the laws, for instance, which means that it is a mistake to think that everyone must have the same general obligation to obey. Nor is every obligation of equal force. Some are weak, such as the notorious obligation to stop at a traffic signal in an isolated area when no one else is around, and others are quite strong. Klosko thus thinks it necessary to rely on the principle of fairness to supply the core of a justification, but to supplement it with appeals to natural duty and the common good (2006, chap. 5).