In Philosophical Foundations of Climate Change, Joseph Heath aims to answer various normative questions that arise when thinking about how governments should respond to climate change. What is the nature of our obligations to future generations? Do we have duties towards non-human life as well? How should we organize society? This is not the first book on these issues, of course; environmental philosophers have been discussing them for decades. Heath's particular aim, however, is to break with – as he perceives it – the tradition of environmental philosophy's irrelevance. According to him, environmental philosophers’ recommendations on what to do about climate change are generally so implausible that they fail to make any productive contribution to the debate at all. This in contrast to economists, who according to Heath ‘always have something useful to say about the relative merits of the policy options that are actually on the table’ (p. 4). While economists are treated with remarkable reverence (they perform ‘deep and careful analysis’ (p. 231) and are anything but ‘stupid’ (p. 74)), environmental philosophers will look in vain for similar thumbs ups in Heath's book. It would be a pity, however, if that deterred environmental philosophers from reading the book. Heath presents a valuable new substantiation of the merits of contractualism to explain our duties to future generations and makes a convincing case that environmental philosophers should take core insights from economics seriously, such as the inevitability of making trade-offs. Heath moreover offers some long-awaited debunkings of misconceptions in the climate debate, such as that economic growth results from present generations saving for future generations instead of being the byproduct of our self-interested savings decisions, and that we can borrow from future generations to finance present climate policy, which in reality we can't.

Unfortunately, Heath's book is not only highly polemical, but also looks for unnecessary fights that distract from the main message with arguments that are often unconvincing. He spends many pages, for example, arguing that environmental philosophers have wasted their time on the question of which entities are ‘morally considerable’. In climate policy, Heath sees no reason to care about non-human life for its own sake, arguing that environmental philosophers disagree on this issue – some want to include all animals, others plants as well – and that their analyses are therefore useless to policymakers. He asserts that boundaries are hard to establish, moreover: ‘How many ganglia must there be in a nerve cluster before we declare it to be a “brain”?’ (p. 28). If we took such arguments seriously, though, it would be equally meaningless to base climate policy on human interests, since philosophers disagree just as much about the boundaries of the human moral community. When does a fetus becomes a ‘person’ and when does abortion become immoral? Heath believes that extending the moral circle is of no relevance at all for the climate debate, moreover, based on the dubious claim that climate change primarily affects humans: ‘The intrinsic values that are threatened in nature pale in comparison to the straightforward loss of human welfare that is projected’ (p. 219). This is an odd claim given the millions to billions of animals that are already being killed by climate-change-induced wildfires and the bleaching of coral reefs, to cite just two examples. Perhaps Heath's claim is due to the strong influence of economic analysis in his book. Since economists assess damage on the basis of willingness-to-pay, it will be of no surprise that human interests predominate in such assessments. In a similar vein, it could be argued that climate change primarily affects the ‘1%’, since the ability-to-pay and thus willingness-to-pay of poor people is negligible.

With equal ease Heath brushes aside the entire debate on ‘climate justice’, namely, the discussion of how the burdens of climate policy ought to be distributed among those presently alive. Once again, Heath argues that the issue is too complex, that there are too many different views, and that it distracts from the ‘primary’ question about efficiency: what global targets should we set and what price should we put on carbon? According to Heath, the ‘only’ questions of distributive justice are how to spend the revenues of a carbon tax and how to allocate permits under a cap-and-trade scheme. The fact that these questions involve the international distribution of several thousand billion US dollars per year and that this immense sum explains the difficulty of international negotiations does not deter Heath from calling it a ‘secondary question’, discussion of which rests on ‘a fundamental misunderstanding of the issue’ (p. 51). Also questionable is Heath's claim that the ‘polluter pays principle’ ‘was never intended to be a principle of distributive justice; it is an efficiency principle’ (p. 62). One of the fundamental insights of Ronald Coase was that it is irrelevant for efficiency whether polluters must compensate the polluted for damage or the polluted must pay the polluters to reduce their pollution. The choice of the ‘polluter pays principle’ in 1972 by the OECD rather than the ‘polluted pays principle’ was therefore explicitly a principle of distributive justice as well.

There are a host of other provocative opinions expressed in this book, such as that sustainable development is essentially an irrelevant concept, since business as usual will already be sustainable. In Heath's view, we should fight climate change and other environmental problems because doing nothing is inefficient, not because they endanger economic growth and future opportunities to be as well off as we are today, nor indeed because they risk destabilizing the very functioning of the global ecosystem as we know it. With regard to the latter, Heath considers discussion of low-probability catastrophic scenarios that might truly endanger future well-being to be largely ‘a distraction’ (p. 66). To the extent that catastrophes are to be feared, Heath proposes we should not let our fear determine efficient mitigation policy, but instead contemplate geoengineering as an emergency measure to interrupt catastrophic feedback processes.

All these issues distract from the interesting and valuable core argument in Heath's book about the nature of our duties to future generations, based on what he calls ‘minimally controversial contractualism’. According to contractualism, the moral qualities of actions are determined by their conformity to principles that no one could reasonably reject and therefore could be the object of unforced agreement. Contractualism appears to solve a number of problems in the intergenerational context. First of all, it solves the problem of ‘demandingness’ that theories such as utilitarianism face. Given the productivity of investments, utilitarianism would recommend directing almost all our income into investments to the benefit of future generations, leaving little for present consumption. No similar duty to increase our savings rate follows from contractualism. Second, contractualism appears to be less vulnerable to the central conundrums in intergenerational ethics: the ‘non-identity problem’ and the ‘repugnant conclusion’. Contractarianism faces its own problem, namely the supposed absence of reciprocity in the intergenerational context. Heath, however, makes a case that there is indirect reciprocity extending indefinitely into the future. How that works is illustrated by a pension scheme financed on a pay-as-you-go basis, where the whole chain of commitments only works on the expectation that the system can continue forever. Given the existence of this indirect reciprocity, Heath believes climate change does not fundamentally differ from other environmental problems such as pollution: it is an ordinary collective action problem where people inflict harm on others without taking this harm into consideration in their decision-making. In economics, such harms are called negative externalities, and the solution is to internalize them using economic instruments like taxation or cap-and-trade systems. There are two reasons why externalities should be internalized. First, externalities are inefficient, that is, they lead to a suboptimal outcome, and second, they are unfair. Not paying for the climate costs of one's actions that fall to future generations would be free-riding, comparable to not paying for the pensions of the retired while one is still employed, while simultaneously intending to make use of the transfers by younger people when one retires oneself. It remains puzzling, however, why Heath believes externalizing climate damage to future generations is unfair (p. 116) while simultaneously believing they are compensated by economic growth (p. 178).

Central to Heath's analysis is the Pareto-efficiency principle, which states that an outcome is to be preferred if it makes at least one person better off without making anyone worse off. As long as the Pareto-efficiency principle is met, no one has reason to complain, and Heath therefore believes the principle logically follows from the idea of contractualism. Heath rejects the Kaldor-Hicks principle, or potential Pareto principle, according to which it is only necessary that people who gain from certain decisions can potentially compensate those who lose. To the extent that cost-benefit analysis is based on the Kaldor-Hicks principle, Heath believes it should be used only in pursuit of actual Pareto improvements, that is, including actual compensation. Given Heath's rejection of Kaldor-Hicks efficiency, it may be wishful thinking for him to state that ‘[w]hat the economist is trying to figure out, by looking at the trade-offs and contemplating the costs and benefits of a carbon abatement policy, is which option provides the best outcome for future generations’ (p. 58). This is incorrect: economists are perfectly happy for future generations to lose under a certain policy, as long as present gains outweigh the (discounted) losses.

Heath spends his last chapter on the thorny issue of the social discount rate, namely, the rate used in cost-benefit analysis to compare future and present changes in consumption. Here Heath's analysis appears to be at odds with his contractarian points of departure. First, he accepts assigning a lower value to future consumption losses compared with present losses to account for the fact that future generations are expected to be wealthier, so that changes in consumption will matter less to them. It is unclear how this aligns with the morality of contractualism and his claim that, because future generations are part of the same system of cooperation as us, ‘our relations with them are governed by the same principles of justice as our relations with contemporaries’ (p. 159). Justice among contemporaries does not require the wealthy to accept exposure to greater risks, certainly not if such risks are left uncompensated. Second, Heath considers it acceptable to attach a lower value to future well-being, that is, to use a positive social time preference. In his discussion he appears to blend contractarian with consequentialist reasoning. Earlier in his book, Heath convincingly shows that his contractarian approach avoids the ‘demandingness’ of utilitarianism by distinguishing harm avoidance from doing good, and that we have a duty to internalize climate damage but no duty to maximize future well-being. Heath therefore needs no positive social rate of time preference to avoid the objection of ‘overdemandingness’. Nevertheless, he turns to the standard consequentialist reasoning of economists such as Tjalling Koopmans to defend a positive social rate of time preference. Heath does not consider this in conflict with treating people as moral equals as long as each generation applies the same rate to all future generations. This is an odd interpretation of moral equality. It would mean that senior students who bully freshmen are treating them as moral equals as long as the freshmen, once they become senior, can do the same to the new batch of students. In fact, Heath proposes a novel justification for attaching a lower value to future well-being: ‘Individuals in their last year of life might be thought of as having “paid their dues,” and thus as exempt from obligations of intergenerational justice’ (p. 262). They have already contributed enough to the intergenerational cooperative scheme. This seems a rather ad hoc position. Up to and including the last unit of consumption at the end of one's life one continues to participate in the intergenerational cooperative scheme. There seems to be no reason why the elderly should be bound less by the principles of fairness.

In conclusion, Heath has aimed to offer philosophical foundations for the kind of climate change policy proposed within mainstream economics. While this may result in recommendations that are readily digestible by policymakers, the philosophical foundations Heath offers are radical within the discourse of environmental philosophy. In combination with Heath's polemical style, it remains to be seen whether he succeeds in ‘promoting greater dialogue’ (p. 23) between philosophers and economists.