Political Liberalism, as we know it today, is not even three decades old. It began to develop in the early 1980s in the writings of several well-known philosophers that included Thomas Nagel, Ronald Dworkin, and John Rawls. The purpose of their project was to offer the political culture an intellectually respectable way to sequester the policy goals of the fledgling movement of religious conservatives while at the same time claiming that their project is consistent with an older liberalism that allows for full political participation by all citizens.
The Political Liberal correctly observes that the differences between citizens on the culture-owar issues – e.g., abortion, marriage, euthanasia – stem from their contrary, though reasonable, worldviews or comprehensive doctrines (as Rawls would put it). Rawls concedes that his understanding of “reasonable” is “deliberately loose.”
“We avoid excluding doctrines as unreasonable,” writes Rawls, “without strong grounds based on clear aspects of the reasonable itself. Otherwise our account runs the danger of being arbitrary and exclusive. Political liberalism counts many familiar and traditional doctrines – religious, philosophical, and moral – as reasonable, even though we could not seriously entertain them for ourselves. . . .” (Emphasis added)
Taking Rites Seriously: Political Liberalism and the Problem of Marriage