Broome (2019) discusses several philosophers who have denied that individual people cause harm via emissions and resultant climate change. He calls these philosophers “individual denialists”. Influential examples include Sinnott-Armstrong (2005), Kingston and Sinnott-Armstrong (2018), and Cripps (2013). I am going to introduce a puzzle for these denialists.
Individual denialism holds that individuals make No Difference:
(No Difference) Individual emissions do not cause morally relevant climate harms.
Broome does appear to disprove this claim. He writes that if we adopt a reasonable (albeit low) social cost of carbon and calculate the implied cost of the emissions, we get measurable, nontrivial costs (on the order of a $1 of social damages for driving your car once for fun for an afternoon). This is a climate harm and it is caused by individual emissions, contra the No Difference claim. (Among others, Hiller 2011 and Nolt 2011 have made similar claims.)
However, many of those who endorse No Difference will deny that Broome has disproven the No Difference claim. They could say, for instance, that what is happening here is that thousands of such actions in large groups do have significant harms, but that apportioning fractions of these harms to individuals commits a fallacy of division. Metaphysically speaking, they could claim, individuals do not ever by themselves cause any harm (cf. Sinnott-Armstrong 2005: “my joyride by itself does not cause the massive quantities that are harmful” (290)).
Before assessing this reply to Broome, we should distinguish No Difference from two other positions:
(No Traceable Difference) Individual emission do not cause any traceable morally relevant climate harms.
Sinnott-Armstrong does not mean this. If he were to say that it is difficult with our scientific knowledge to attribute specific climate harms to specific individuals, then one could not seriously object.
(Some Difference) Individual emissions do not sometimes cause morally relevant climate harms.
Sinnott-Armstrong does not mean this, either. If he were to say individuals cause morally relevant harms, but not every time they emit, then it would again be hard to object to that.
By contrast, here is a view that Sinnott-Armstrong and many other individual denialists do accept:
(Group Difference) National and global emissions do cause morally relevant climate harms.
But now there is the puzzle for the Denialists. While No Difference says that individuals have no causal climate impact, Group Difference says national groups do have causal climate impact; these claims together generate tension. It would be more natural to say either that both individuals and groups do or that both do not have an impact. So here is the puzzle for the denialist to explain:
(Difference) There is a difference between groups and individuals which gives rise to Group Difference and No Difference.
Unlike Broome, I am going to grant Sinnott-Armstrong and the other Individual Denialists the claim that there could be some metaphysical threshold such that some large number of actions are sufficient to cause morally relevant climate harms, but that no subsets of those actions cause morally relevant harms at all. I want to engage the individual denialists on their most favorable terrain. I still think we can show that accepting Difference is unjustified.
To assess the denialists’ puzzle, consider two ways one might come to know Difference, a priori and a posteriori:
(A Priori) We know Difference a priori.
A Priori appears implausible. We certainly do not know that the climate system exists a priori; it would be incredible if we knew how it works a priori. Furthermore, there is nothing analytic about the notion that an individual’s emissions have no causal contribution to climate change.
There are closely related claims we might know a priori: for instance, some might think that we know a priori that individuals are a particularly morally relevant (or at least a morally salient) category. However, that does not suffice to justify A Priori.
(A Posteriori) We know Difference a posteriori.
Here are two ways we might defend A Posteriori:
(Natural Language Datum) Difference is a truth of natural language.
When considering whether a grain or a thousand grains of sand makes a heap, we appeal to actual language use. However, whether you take individuals to make a causal difference to climate change is not intuitively a matter for natural language use. Neither is whether groups do. These are matters upon which we refer to natural science, not to language users’ usage of the terms. This brings us to:
(Climate Science Datum) Difference is a truth of climate science.
This is, I believe, the most plausible basis Individual Denialists could use to support Difference. Difference is, at its heart, an empirical scientific claim. Unfortunately, no defenders of Difference have attempted to defend it scientifically. There is good reason for this: climate science has not shown Difference to be true! At best, our current science supports No Traceable Difference. But absence of evidence is not evidence of absence.
From a scientific point of view, there is nothing privileged about the level of emissions of individuals. Even granted that there could be such a threshold, why would it be between nations and individuals? Why not between nations and regions? Or regions and towns? Or individuals and time-slices of individuals? Even granted that there could be such a threshold, there are many potential orders of magnitude where the threshold could occur.
There is no evidence or reason that the scientific results would carve up emissions between individual emissions and aggregated national emissions such that the Difference-making threshold happens to be between the two levels the individual denialist claims. Without such support, Difference is unjustified.
I have granted arguendo that Difference is a metaphysical possibility. But insofar as it remains unjustified and is merely asserted without any way of knowing whether it is the case, it is absurd to base our reasoning on it. When considering potential harm to others, we should adopt a higher bar of justification.
fallacy of division: reasoning where a characteristic of the whole is invalidly applied to parts
a priori: knowledge that does not require experience of the actual world to justify it (e.g. “7 x 3 = 21”)
a posteriori: knowledge that does require experience of the actual world to justify it (e.g. “Pluto is not a planet”)
analytic: when a claim is true merely in virtue of the meaning of the words (e.g. “Nieces are female”)
arguendo: for the sake of argument
Broome, J., (2019). Against Denialism. The Monist, 102(1), pp. 110–129. doi:10.1093/monist/ony024
Cripps, E., (2013). Climate Change and the Individual Agent. Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199665655.001.0001
Fleurbaey, M. et al., (2019). The Social Cost of Carbon: Valuing Inequality, Risk, and Population for Climate Policy. The Monist, 102(1), pp. 84–109. doi:10.1093/monist/ony023
Hiller, A., (2011). Climate Change and Individual Responsibility. The Monist, 94(3), pp. 349–368. doi:10.5840/monist201194318
Kingston, E. & Sinnott-Amstrong, W., (2018). What’s Wrong with Joyguzzling? Ethical Theory and Moral Practice, 21(1), pp. 169–186. doi:10.1007/s10677-017-9859-1
Mintz-Woo, K., (2018). Two Moral Arguments for a Global Social Cost of Carbon. Ethics, Policy & Environment, 21(1), pp. 60–63. doi:10.1080/21550085.2018.1448038
Nolt, J., (2011). How Harmful Are the Average American’s Greenhouse Gas Emissions? Ethics, Policy & Environment, 14(1), pp. 3–10. doi:10.1080/21550085.2011.561584
Sinnott-Armstrong, W., (2005). It’s Not My Fault: Global Warming and Individual Obligations, in Sinnott-Armstrong, W. & R. Howarth (eds.) Perspectives on Climate Change. Oxford: Elsevier. pp. 285–307.