This is a new paper in the Global Priorities Institute working paper series by Jacob Barrett (Global Priorities Institute, University of Oxford) and Andreas T Schmidt (University of Groningen).


 Moral uncertainty and disagreement pervade our lives. Yet we still need to make decisions and act, both in individual and political contexts. So, what should we do? The moral uncertainty approach provides a theory of what individuals morally ought to do when they are uncertain about morality. Public reason liberals, in contrast, provide a theory of how societies should deal with reasonable disagreements about morality. They defend the public justification principle: state action is permissible only if it can be justified to all reasonable people. In this article, we bring these two approaches together. Specifically, we investigate whether the moral uncertainty approach supports public reason liberalism: given our own moral uncertainty, should we favor public justification? We argue that while the moral uncertainty approach cannot vindicate an exceptionless public justification principle, it gives us reason to adopt public justification as a pro tanto institutional commitment. Furthermore, it provides new answers to some intramural debates among public reason liberals and new responses to some common objections.


Moral disagreement pervades our lives. We disagree about the rightness or wrongness of actions, the goodness or badness of outcomes, and the justice or injustice of institutions. These disagreements often seem quite reasonable – and equally intractable. Moral reasoning is hard, requiring us to navigate complex concepts and their intricate and often surprising implications. We come to this task with different life experiences, educations, and social networks, and so with different biases, priors, and evidence bases. And even when we agree about the considerations at issue in some case, we often disagree about their weights. Moral thinking, in other words, is subject to the “burdens of judgment” ((Rawls 2005, 55–57); compare (MacAskill, Bykvist, and Ord 2020, 11–14)). And it is a predictable consequence of these burdens that intelligent people reasoning in good faith will come to different conclusions about morality. 

Given the many plausible moral views available to us, and their many capable and eager champions, it is difficult to know how to proceed. We must reckon both with the fact of our own uncertainty about morality, and with the fact that others will inevitably come to different conclusions than we do. These two facts, though closely related, have spawned two very different research programs in contemporary analytic philosophy: public reason liberalism in political philosophy and the moral uncertainty approach in ethics. Public reason liberals ask what laws are justified among individuals who reasonably disagree about morality. They argue that we should take all reasonable positions into account – holding that a law is justified not when the moral view we find most plausible says it is, but when the law can be justified to all reasonable people. Moral uncertainty theorists are concerned with what we morally ought to do in the face of our own uncertainty about morality. They argue that we should take all plausible moral positions into account – holding that what we morally ought to do depends not only on the moral theory we find most plausible, but also on the verdicts of all other moral theories in which we place some positive credence. 

Our goal in this article is to bring these research programs into contact. To frame our 3 discussion, we investigate the hypothesis that the moral uncertainty approach lends support to public reason liberalism. Our tentative conclusion is that while the moral uncertainty approach cannot vindicate the stringent principle that all laws be publicly justified, it nevertheless provides several reasons to take public justification seriously. Specifically, from the perspective of moral uncertainty, a good case can be made for treating public justification as a weighty pro tanto institutional commitment – albeit one that can be overridden when the moral stakes are high. 

Along the way, we also highlight some attractive features of our novel defense of public justification. For example, critics often argue that existing defenses of the public justification principle fail to cohere with the principle itself, because they assume controversial first-order views about morality or justice, either explicitly or in the way they narrowly delineate the class of “reasonable” people. The moral uncertainty approach sidesteps this issue, because it permits uncertainty about morality and justice all the way down and relies on a thin and independently motivated notion of reasonableness. Moreover, the moral uncertainty approach offers a fresh perspective from which to resolve some contested intramural debates among public reason liberals, not only about when to count someone as reasonable, but also about what it takes to justify a law to a reasonable person, and about the role of “shared reasons” in public justification. 

We proceed as follows. In section 2, we outline public reason liberalism and the moral uncertainty approach and introduce our hypothesis. In sections 3, 4 and 5, we discuss arguments in support of this hypothesis. We comment on intramural debates on public justification in section 6 and conclude in section 7.

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Would you be able to provide a plainer language summary of the papers conclusions or arguments? I think I'm interested in the topics discussed in the paper. But it’s unclear me what the arguments actually are, so I’m inclined to disengage. 

Take this sentence, which seems important: 

“We argue that while the moral uncertainty approach cannot vindicate an exceptionless public justification principle, it gives us reason to adopt public justification as a pro tanto institutional commitment.”

I do not understand this and so I do not see how this is a valuable addition to the critical topic of moral uncertainty.

I know this doesn't solve the actual problem you're getting at, but here's a translation of that sentence from philosophese to English. "Pro tanto" essentially means "all else equal": a "pro tanto" consideration is a consideration, but not necessarily an overriding one. "Public justification" just means justifying policy choices with reasons that would/could be persuasive to the public/to the people they will affect. So the sentence as a whole means something like "While moral uncertainty doesn't mean that governments (and other institutions) should always justify their decisions to the people, it does mean they should do so when they can."

Oops, one correction: "public justification" doesn't mean "justification to the people a policy will affect", it means "justification to all reasonable people"; "reasonable people" is roughly everyone except Nazis and others with similarly extreme views.