The Nature of the Constraint
Let us begin with how the constraint is understood. The first problem is that the quasi-economic label “Paretianism” is misleading. Traditional Pareto optimality picks out an (ethically loaded) sense of efficiency: no one can be made better off without making someone else worse off. Intuitively, this rules out a certain kind of waste: in a Pareto inefficient situation, at least one person can be made better off without making anyone worse off.
By contrast, the Chicago constraint makes the very different claim that all states must benefit. Call this, “International Mutual-Benefitism” (IMB). IMB has nothing to do with eliminating waste. For one thing, it is compatible with wasteful violations of Pareto optimality (e.g., a weak climate treaty might benefit everyone, but much less so than a strong climate treaty). For another, it rules out some Pareto improvements (e.g., climate policies that benefit only some [e.g., poor countries], but make others [e.g., the rich] no worse off).
The second problem is that, as stated, IMB does not specify a baseline against which the better off judgment is to be made. There are many possibilities: better off than under a climate catastrophe; better off than now; better off than if all continue to emit freely in the future; etc. Which is chosen makes a huge difference. For instance, at one extreme, “better off than catastrophe” might be easy to achieve, but of little interest to anyone (e.g., a treaty that saved one acre of the Maldives might make them slightly better off than losing everything, but remains unlikely to secure their consent); at the other extreme, “better off than under any alternative” might lead every nation to hold out for a deal where others do all the mitigation, and so not be feasible. Moreover, we should consider the possibility that the most relevant baseline might be ethical. For instance, countries might refuse to consent to treaties that treat them unfairly, are inconsistent with basic norms of self-respect, do not pay adequate respect to their interests (e.g., the basic human rights of their citizens, their right to escape extreme poverty), and so on.
The third problem is that the strength of IMB is radically underdetermined. Though the language of constraint suggests that self-interest limits the role of other factors, economic realists often vacillate on how sharp this limit is. First, at one extreme, self-interest might decisively determine what can be done (e.g., we do not need ethics to tell us to get out of the way of a moving train). Here, the “constraint” is really an absolute prohibition: ethics is irrelevant because there is no room for it.
Second, more moderate versions of IMB assert only that perceived self-interest restricts the role of ethics. For instance, Posner and Weisbach sometimes claim that International Paretianism (IP) “will generate a surplus— the climatic benefits minus the costs of abatement,” and concede both that IP has “nothing to say” about distributing this surplus, and that distribution can be done “on the basis of ethical postulates.”11 The crucial question for restrictive views is how extensive the allowed zone is. If it is small, restriction is very close to determination; if large, ethics can make a substantial contribution.
Initially, Posner and Weisbach’s main rationale for the surplus implies that the zone available for ethics is very large. They argue that mitigating “creates a surplus relative to the status quo,” since “scientific evidence strongly suggests that humanity will be worse off in the future if climate mitigation efforts are not made.”12 This suggests that the relevant baseline for IMB is how well off people are now. Yet mainstream economic analyses suggest that the costs of climate action (at roughly 1% of global product) are considerably lower than those of future climate damages (up to 20%), and also by comparison to the benefits of future economic growth in the absence of climate change (2%-4% annually if the past is a good guide). In short, the future benefits of avoiding severe climate change are so large that not making any country worse off than it is now appears a relatively minor constraint, leaving plenty of room for ethics.
Still, elsewhere Posner and Weisbach apparently reject this optimistic scenario, insisting that ethical principles
“can at best play a modest role” in treaty negotiations, and “most likely [affect] only a small portion of the surplus.”13 This suggests more restrictive (and ethically worrying) baselines. For instance, a second gloss on maintaining the “status quo” would incorporate current expectations for the future, including those based on unconstrained fossil fuel use (e.g., climate action “must make people as well off if they comply as if they cheat”14). Worse, a rival benchmark would have current governments seek to maximize their gains from a treaty, and so pursue the largest possible portion of the surplus that they can get. This may leave no room for ethics.15 Though they officially reject maximization, Posner and Weisbach concede that they cannot rule it out, and many economic realists accept it.
Third, at the opposite extreme, a very different interpretation of IMB would regard perceived self-interest as itself determined by ethical values, on the grounds that ethics is essential to how we conceive of ourselves (cf. Keynes’ remark that “the world is ruled by,” and “practical men ... slaves to ... ” the ideas of economists and political philosophers). This view is in serious tension with both the “ethics vs. policy” strand, and the claim that philosophy lacks the relevant tools for policy. For instance, it suggests that philosophical reflection might change a nation’s perception of its interests by (for example) enabling it to see that its initial perception is wrong in light of values it already has, causing it to rethink how it understands those values, or spurring it to revise or add to those values. This is to concede a very large role for ethics and philosophy.
Of course, even here, the role of ethics remains officially constrained by the confines of a conception of “perceived self-interest” within which wider values play a role. (So we have the surprising result that “perceived self-interest” swallows ethics whole, at least from the practical point of view.) Nevertheless, this limitation may be merely verbal: if ethical values are constitutive of perceived self-interest, “perceived self-interest” may be sufficiently malleable to accommodate virtually any content. If so, the much vaunted feasibility constraint may be more or less empty, a rhetorical gloss that can be placed on any appropriate scheme, but one that provides no restrictions, and so no real constraint.