This essay shows the continued value of Rawls’s public reason project. Its internal tendency is to generate new ideas. To do so, I review seven models of public reason, beginning with A Theory of Justice. Following Political Liberalism, I focus on Rawls’s unaddressed problem of justice pluralism. Rawls did not contain reasonable disagreement abou tjustice. Failing to stop it requires developing a fourth model of public reason. If Rawlsians accept justice pluralism, they must explore Gerald Gaus’s public reason project, so I introduce three models of public reason in Gaus’s work. The final model has only begun to bear fruit, generating a research program Gaus called the New Diversity Theory. Rawls and Gaus show that the public reason project remains a fertile research program

We are familiar with one divide between “old” and “new” liberalism – that between classical liberalism and social justice liberalism. Although this divide between the old and the new is multifaceted, the crux is a debate about the place of the market, private property, and democracy in a liberal polity. According to common wisdom, classical liberals insist on rights of the person against others and against a limited government, freedom of association, freedom of conscience, and a free market within a framework of laws against fraud and violence, laws enforcing contracts, and strong rights of private property, including robust rights of investment, exchange, and inheritance. Limited democracy is endorsed as a way to control government, but not as a source of fundamental norms. Social justice liberals, while endorsing traditional civil rights – for example, the freedoms of speech, press, and religion, rights against search and seizure, the right to a fair trial, privacy rights, equal protection of the laws, and, generally, liberties of the person – argue that justice fundamentally concerns the distribution of resources or that one’s basic claims of justice are to resources that one needs or deserves. Thus, such liberals lay great stress on policies to alter the distribution of property, or to enforce social rights to assistance. Moreover, such liberals emphasize the role of democratic institutions in a liberal polity. Indeed, in recent years, social justice liberals such as John Rawls and his followers have declared themselves to be “deliberative democrats,” who value political participation rights equally with civil liberties. While of course inadequate, this familiar stylized contrast between classical liberalism and social justice liberalism captures a good deal of the truth.

Gerald (“Jerry”) Gaus was a distinguished political philosopher who died unexpectedly in August of 2020. Indeed, he died within days of finishing his final book, The Open Society and Its Complexities. The book adds further depth to Gaus’s corpus, which has received increasing attention over the last twenty years. Awareness grew quickly after Gaus published his magnum opus, The Order of Public Reason, in 2011.

John Rawls’s political liberalismis best understood as a response to the fact that the free exercise of human reason in modern democratic societies leads us to embrace a ‘diversity of reasonable comprehensive doctrines’. Because of this, Rawls insists, any (successful) attempt to unite society on a shared comprehensive doctrine requires the oppressive use of state power to suppress competing, reasonable, comprehensive doctrines. If we are to achieve unity without oppression we must ‘all affirm’ a public political conception (PL: 38) that is supported by, or at least does not conflict with, the diverse reasonable comprehensive doctrines that characterize our democratic societies. This political conception is a ‘module’ that fits into our many reasonable, irreconcilable, comprehensive views. And because this political conception can be affirmed by all reasonable comprehensive doctrines, oppressive state power is not required to uphold it.

It is an honor and a treat when innovative social theorists and philosophers take time out of their important work to think about one’s own. The set of papers being published in COSMOS + TAXIS are especially flattering. Fred D’Agostino, Blain Neufeld, Scott E. Page, Kevin Vallier, Lori Watson and David Wiens all constructively engage The Tyranny of the Ideal and open up new issues to be explored. I am especially grateful to Ryan Muldoon for organizing this symposium (and, I should say, for all his work from which I have learned so much). I am also delighted that the symposium appears in COSMOS + TAXIS because the main theme of the book, which I hope to emphasize here (and which D’Agostino and Page bring out wonderfully in their essays) is that the subject matter of social philosophy is complex systems, something Hayek (1964 [2014], chap. 9) was one of the first to stress. Until, as Page puts it, “the imperative of complexity” is appreciated by political philosophers their work will remain what Hayek warned against – constructivist fantasies in which the critical problems of evaluative diversity, path-dependency, uncertainty, and interconnectedness are assumed away.

In the last few decades, a new conception of liberalism has arisen – “justificatory liberalism” – which developed out of the social contract tradition. The social contract theories of Thomas Hobbes, John Locke, and Jean-Jacques Rousseau all stressed that the justification of the state depended on showing that everyone would, in some way, consent to it. By relying on consent, social contract theory seemed to suppose a voluntarist conception of political justice and obligation: what is just depends on what people choose to agree to – what they will. As David Hume famously pointed out, such accounts seem to imply that, ultimately, political justice derives from promissory obligations, which the social contract theory leaves unexplained. Only in the political philosophy of Immanuel Kant, I think, does it become clear that consent is not fundamental to a social contract view: we have a duty to agree to act according to the “idea” of an “original contract” to which all agree. John Rawls’s revival of social contract theory in A Theory of Justice did not base obligations on consent, though the apparatus of an “original agreement” of sorts persisted. The aim of his famous “original position,” Rawls announced, was to settle “the question of justification … by working out a problem of deliberation.” As the question of justification takes center stage (we might say: as contractualist liberalism becomes justificatory liberalism), it becomes clear that posing the problem of justification in terms of a deliberative problem or a bargaining problem is a heuristic: the real issue is “the problem of justification” – what principles can be justified to all rational and reflective persons seeking to live under impartial principles of justice.

Public reason liberalism is a family of theories according to which liberal political institutions, social structures, and/or basic social rules are politically or morally justified if and only if they can be endorsed from the perspective of each and every free and equal “reasonable and rational” person. Let us call these persons “the members of the justificatory public.” Public reason liberalism idealizes the members of the justificatory public in three senses. First, the members of the justificatory public are assumed to be free from at least some of the cognitive distortions and biases that often characterize actual people; we suppose that they generally reason in a sound way on the basis of relevant information. Different versions of public reason liberalism press this idealization quite far, while others insist on a “moderate idealization.” Secondly, the members of the justificatory public are idealized insofar as it is assumed that each is a good-willed person, concerned with living with others on terms that are mutually acceptable. In Rawls’s language, we suppose that they are not simply rational, but “reasonable”: they have a form of “moral sensibility” according to which they are ready to propose fair terms of cooperation, and are willing to abide by them “provided others can be relied on to do likewise.” The members of the justificatory public are thus idealized insofar as they are assumed to be moved by their sense of justice, or their aim to respect others as free and equal persons. This leads to a third idealization: by assuming that the members of the justificatory public are moved by this moral sensibility, it is supposed that they do not pay attention to their reasons to ignore their sense of justice (or, we might say, defect on moral arrangements when doing so better advances their cherished ends, aims, and projects). More generally, any specific version of public reason liberalism will hold that some reasons of actual people are not relevant to the justificatory question: the members of the justificatory public “bracket” (i.e., set aside) these reasons in their deliberations.

Contemporary moral and political philosophy is torn between two modes of moral reasoning. A common view of moral thinking – perhaps most characteristic of moral philosophy – understands reasoning about moral claims to be, in a fundamental sense, akin to reasoning about ordinary factual claims. On this commonsense approach, when Alf deliberates about a moral claim or demand (say, that people ought to respect property), he considers the best reasons as he understands them for and against the claim, including what he takes to be the correct normative principles, perhaps checks his conclusions with others to see if he has made any errors, and then comes to the conclusion, ‘we all ought to respect property’. His moral reasoning may refer to facts about other people (say, their welfare), but it is not a general requirement on the moral reasoning of any competent agent that he always takes as one of his inputs the moral deliberations of others.

My concern in this essay is a family of liberal theories that I shall call “public reason liberalism.” Fundamental to public reason liberalism is the commitment to the moral equality of all persons. Because we are equal moral persons, morality must be justified to all. Public reason liberalism is not to be equated with political liberalism. The latter is a specific version of public reason liberalism that seeks to restrict the set to be justified to a small number of principles of political right that are largely independent of moral principles. Rawls’s earlier work – certainly his 1951 essay “Outline of a Decision Procedure in Ethics” and the famous essay on “Justice and Fairness” – understood the subject of justification more expansively, focusing on what we might call “social ethics,” i.e., the moral resolution of competing claims of individuals. On this view liberalism is not simply a theory of the justice of the basic structure of society, but a public moral framework by which individuals can adjudicate their conflicting claims and demands on one another. Some may call this is a “comprehensive” liberalism, but we should be wary of such a simple description. Much of what we call “ethics” – including visions of the good life and conceptions of virtue and vice – lies outside social morality. As J.S. Mill saw it, the subject of “Civil” or “Social Liberty” – which is plausibly the subject of liberalism – involves the nature and limits of the moral authority of society over individuals to insist that they refrain from speaking, acting, and living as they wish. It is this broader understanding of liberalism that is my focus. Public reason liberalism, as I conceive it, claims that the principles of social or public morality that allow one individual to make demands on others to act or desist from acting must be justifiable to each and every reasonable moral person within that community.