Can’t we all just get along? Can’t we just set religious, moral and philosophical differences aside and let politics be just politics? This is a wish that has animated modern political theory since the days of Machiavelli and Hobbes. The fullest expression of this wish in more recent liberal political theory is certainly the work of the late Harvard professor John Rawls, who spent a whole, brilliant career trying to expunge the last traces of any “comprehensive views” (that is, unprovable religious or philosophical predilections) from his “political liberalism.”

His failure to attain the Shangri-La of religious and philosophic neutrality, after decades of revisions and re-revisions of his monumental system, teaches a lesson that contemporary liberalism still needs to learn.

With the publication of "A Theory of Justice" in 1971, Rawls went from being another well-respected academic philosopher to the leader and the subject of a whole new industry in liberal political theory. Rawls proposed a theoretical framework for modern, post-New Deal redistributionist liberalism that would give it the philosophical prestige and conceptual amplitude of canonical authors such as John Locke and Immanuel Kant.

The central conceit of his grand new system was the notion of the “Original Position,” a new, abstract conception of the classic “social contract,” one in which the parties to the agreement on fundamental political principles would be put behind a “veil of ignorance” that would conceal from them not only features considered morally accidental such as race, sex and socio-economic status, but even their very “conceptions of the good” — their most basic religious or philosophic convictions. In this way, Rawls proposed to conceptualize the modern liberal idea of a political system totally independent of traditional moral and religious beliefs.

Rawls’ "Theory" was a stupendous success; it gave rise to a whole industry of commentary and application, and its influence spread well beyond departments of philosophy into the social sciences and, especially, law schools and judicial interpretation. But eventually certain of Rawls’ friendly critics convinced him that he was not liberal enough, since the last third of his book seemed to want to base his idea of justice on his own favored personal morality, a certain idea of moral freedom or “autonomy” redolent of Kant’s moral philosophy.

Rawls had in fact concluded "A Theory of Justice" with a striking rhapsody to a secular understanding of Protestant “purity of heart.” To achieve true purity of heart, for Rawls, is to overcome religious prejudice and to translate pure autonomy or self-ownership into service to the secular good of humanity.

Impressed by critics who found that his liberalism was tainted by a personal moral perspective, Rawls set about further neutralizing his theory, an effort that culminated in his "Political Liberalism" of 1993. The title says it all: rather than succumbing to the temptation to base liberalism on some underlying philosophy (such as personal autonomy), Rawls would limit his aim to a purely political liberalism — nothing about the meaning of life here, he insists, just a convenient doctrine for helping us all to get along in a liberal, pluralist society.

Wouldn’t that be nice — a way to agree politically without having to come to terms with deeper moral and religious disagreements. If that sounds too convenient to be true, it is. When it comes down to actual cases, Rawls is still ready to put the force of law behind some citizens’ basic moral views and to require others to privatize their convictions. His famous notion of “public reason” favors liberals who hold personal freedom to be the highest ideal, while traditional religious believers who are opposed to abortion, for example, are excluded, in the name of “fairness,” from the public square.

It turns out that Rawls’ own belief in personal autonomy as the be-all and end-all of morality could not be bracketed after all. Rawls’ moral resoluteness (if not the breadth of his sympathies) is to be admired, for he indeed spent an illustrious career of 50 years at Harvard pursuing a secular purity of heart, and yet managing to convince himself and generations of Rawlsian theorists and their acolytes in the law schools that he had squared the circle, found a formula to separate political morality from “comprehensive view” about the meaning of life.

The dream of a morally neutral political theory is a delusion. Rawls’ project fails because he is a human being moved, like the rest of us, by a certain idea of the meaning of life — in his case by a humanitarian ideal, a this-worldly “purity of heart” that implies its own “comprehensive view” of human meaning. Aristotle, it turns out, is a better guide to managing the “pluralism” of political opinions — but that’s another tale to tell.

Ralph Hancock is a professor of political science at Brigham Young University and president of the John Adams Center for the Study of Faith, Philosophy and Public Affairs. His opinions do not necessarily reflect those of BYU.