Modern convention and habits are no excuse. Liberalism is heresy.
Which liberalism?
a movement in modern Protestantism that emphasizes freedom from tradition and authority, the adjustment of religious beliefs to scientific conceptions, and the development of spiritual capacities.
or
a political or social philosophy advocating the freedom of the individual, parliamentary systems of government, nonviolent modification of political, social, or economic institutions to assure unrestricted development in all spheres of human endeavor, and governmental guarantees of individual rights and civil liberties.
Of course there are far more definitions, but I expect you're either working with the philisophica\political idea of libralism or the theological one.
It could just be:
In the twentieth century, a viewpoint or ideology associated with free political institutions and religious toleration, as well as support for a strong role of government in regulating capitalism and constructing the welfare state.
Really you could mean any of those, or a combination of them, I'm just wondering what you specifically mean.