Political Liberalism was motivated by Rawls's belief that A Theory of Justice inadequately treated the problem of stability. Theory of Justice grounded justice in a comprehensive doctrine, ethical liberalism. In a society wherein citizens hold a variety of reasonable comprehensive doctrines, such a theory of justice is unstable. Political Liberalism seeks a free-standing political theory compatible with many reasonable comprehensive doctrines.
Reasonableness involves reciprocity which in turn requires the acceptance of the burdens of judgment. We cannot respect other citizens if we regard them or their comprehensive doctrines as pernicious or stupid. While we may continue to accept our own comprehensive doctrine, reciprocity and tolerance require that we recognize that other doctrines and those who hold them are reasonable.
Callan claims that Rawls's project fails. Ethical liberalism views autonomy as essential to a good life. However, if the burdens of judgment are a prerequisite for reciprocity, political liberalism must also value autonomy, if not as an essential part of a good life, then as a public good. Any view of political socialization robust enough to secure a recognition of the burdens of judgment must also produce habits of mind tantamount to autonomy. If so, political liberalism collapses into ethical liberalism. Their implications for political socialization are indistinguishable. Many comprehensive doctrines, paradigmatically religious ones, will be weakened by these requirements for political socialization.
Callan's argument points to a tension in liberal views of education. A liberalism that promotes a thick liberal culture will appear intolerant to many with religious commitments.