On the survival of humanity

Abstract

What moral reasons, if any, do we have to ensure the long-term survival of humanity? This article contrastively explores two answers to this question: according to the first, we should ensure the survival of humanity because we have reason to maximize the number of happy lives that are ever lived, all else equal. According to the second, seeking to sustain humanity into the future is the appropriate response to the final value of humanity itself. Along the way, the article discusses various issues in population axiology, particularly the so-called Intuition of Neutrality and John Broome’s ‘greediness objection’ to this intuition.

Keywords:

• Population ethics
• axiology
• survival of humanity
• intuition of neutrality
• John Broome

Acknowledgments

For their generous help and feedback on earlier drafts of this article, I would like to thank Nick Beckstead, Luc Bovens, Krister Bykvist, Ruth Chang, Partha Dasgupta, Louis-Philippe Hodgson, Tom Hurka, Mark Johnston, Frances Kamm, Christine Korsgaard, Eden Lin, Elinor Mason, Kian Mintz-Woo, Ekédi Mpondo-Dika, Derek Parfit, Philip Pettit, Theron Pummer, Mozaffar Qizilbash, Melinda Roberts, Geoff Sayre-McCord, Alison McQueen, Tim Scanlon, Alec Walen and Monique Wonderly, as well as audiences and workshop participants at Harvard University, the University of Oxford, Princeton University, and the University of Toronto. Finally, I would like to thank my hosts at the University of Toronto Centre for Ethics, where I completed this article.

Notes

1. My constructive proposal will not take a stand on how weighty these moral reasons are, nor on what, exactly, they are reasons to do. Before we can sensibly attack these issues, we must first resolve the more fundamental question whether there are any genuinely moral reasons to ensure the survival of humanity in the first place. This is the task I set myself in this article.

2. Early versions of this argument are found, inter alia, in Glover (1977), Kavka (1978), and Parfit (1984).

3. In keeping with established practice in population ethics, I employ the phrases ‘a happy life’ and ‘a miserable life’ as synonyms for ‘a life worth living’ and ‘a life not worth living’. In so doing, I do not take a stand on what, exactly, makes a life worth living or not worth living for a person. That is, I shall remain agnostic with regard to the correct theory of well-being (which I understand as that which makes a person’s life go well or, at least, worth living).

4. The qualification ‘all else equal’ in premises (1), (2), (4) and the conclusion is necessary in order to account for the possibility that, despite making the world better in one respect, the longer survival of humanity makes the world worse all things considered, for instance by greatly increasing suffering among non-human animals. In the following, like most proponents of the Argument from Additional Lives, I shall bracket this possibility. I thank Krister Bykvist for discussion of this point.

5. See Frick (2014, Chapter 2).

6. For discussions of this point, see Glover (1977, 69–71) and Broome (2004, 126–128). See Footnote 11 for why, strictly speaking, Broome is not himself a proponent of the Argument from Additional Lives.

7. This lower bound may correspond to the level of wellbeing at which a life becomes not worth living for that person herself; but on some views – so called critical level theories – the level of wellbeing below which adding an extra person to a population makes the outcome worse may be considerably higher than the boundary between a life worth living and a life not worth living. Broome (2004) defends a form of critical level theory.

8. If there is an upper bound to the neutral range, this implies that there is some threshold of personal value such that creating a new life above that threshold makes the world better. There are also other possibilities: if we are perfectionists, we may hold that there are some individuals whose existence makes the world better on account of their extraordinary achievements or because their lives are excellent in some other regard – irrespective of the amount of wellbeing that these lives contain. We may believe, for instance, that the existence of van Gogh or Kafka made the world better on account of their extraordinary artistic achievements – not because they had lives that went especially well for them, all things considered.

9. The Procreation Asymmetry was first discussed by Narveson (1967). The label is due to McMahan (1981). I defend the Procreation Asymmetry at length in my article ‘Conditional Reasons and the Procreation Asymmetry’ (unpublished manuscript).

10. Nota bene: That Broome believes we must give up the Intuition of Neutrality does not mean that he himself endorses the Argument from Additional Lives. Broome stops short of endorsing this argument since he is, for the time being, agnostic about where the single neutral level of existence is located (Broome 2005, 208). Without further work in population ethics, Broome believes, we are not at present in a position to know whether the absence of worthwhile lives due to the premature extinction of humanity would make the world worse or better (though Broome certainly inclines to the former belief). What we can know, contra the Intuition of Neutrality, is that the absence of such a large number of worthwhile lives is likely to be ethically highly significant – one way or the other. As Broome puts it in his recent book Climate Matters: ‘Because the intuition of neutrality is false (…) we cannot assume that all those absences are neutral in value. We must expect the absences to be either a good thing or a bad thing. Intuitively it seems most plausible that they are bad. We mostly feel that (…) extinction would be a very bad thing indeed. But (…) we still have a lot of work to do before we can be sure that is so’ (Broome 2012, 183).

11. For an ingenious recent attempt to defend the equality-interpretation of the intuition of neutrality against Broome’s critique, see Melinda Roberts, ‘The Neutrality Intuition’ (unpublished manuscript).

12. Broome’s term ‘incommensurateness’ is ambiguous between two readings: Incommensurateness, as Broome defines it, states only the absence of any of the standard trichotomy of evaluative relations. This leaves two options: either the two items are incomparable in value, or they are connected by a fourth positive value relation, for example Chang (2002) notion of ‘parity’. None of Broome’s arguments against the incommensurateness-interpretation seem to turn on adopting one reading rather than the other. By contrast, the case for the incommensurateness-interpretation seems to me strongest when it is cashed out in terms of parity. So that is the reading I will assume in the following.

13. In the following, I restate, in axiological terms, points which I develop at much greater length in ‘Conditional Reasons and the Procreation Asymmetry’.

14. More precisely: The conditional value of wellbeing is conditional on existence, but it is not conditional on the identity of those who exist. This claim is necessary in order to avoid Parfit’s (1984) Non-Identity Problem. Thus, in the following same-number case.

P = (5, 3, Ω).

Q = (5, Ω, 5).

we can say that distribution Q is impersonally better than P, since it does better by the people who exist in it, although the persons who exist in P and Q are not identical.

15. I here follow, step for step, Broome’s presentation of the argument in his article ‘Should We Value Population?’, The Journal of Political Philosophy, Vol. 13, No. 4 (2005), in particular pp. 407–411. A shorter statement of the Argument from Greediness occurs in Weighing Lives, pp. 169–170.

16. Broome (2004) also advances a second argument against incommensurateness interpretation, to wit that the boundaries of the neutral range must surely be vague, but that such vagueness at the boundaries is incompatible with the intuition of neutrality understood as incommensurability. This argument is convincingly rebutted by Rabinowicz (2009), so I will not review it here.

17. The same example could also be be used to show that the equality interpretation of neutrality, which we discussed above, is likewise greedy. I leave this as an exercise for the reader.

18. In his most recent discussion of the Intuition of Neutrality in Climate Matters, Broome – perhaps in response to Rabinowicz’s critique – appears to build the Non-Greediness Principle into his statement of the Intuition of Neutrality itself. Thus, he writes: ‘Suppose two alternative options A and B have just the same population of people, except that there are some people in B who do not exist in A. Call the people who exist in both A and B ‘the existing people’ and others ‘the added people’. The intuition [of neutrality] is that there is a neutral range of well-being such that, provided the added people’s well-being is within the neutral range, the following is true: if B is better than A for the existing people, then B is better than A, and if B is worse than A for the existing people, then B is worse than A.’ (Broome 2012, 176). This characterization of the Intuition of Neutrality, which includes the Non-Greediness Principle by default, is a significant departure from Broome’s earlier statements of the intuition, such as the one I quoted in Section 3. According to that earlier statement, it is a sufficient but not a necessary condition for the move from O₁ to O₂ to be axiologically neutral that O₂ is neither better nor worse in its effects on the original people. Since I will go on to argue, contra Broome, that the most plausible specification of the Intuition of Neutrality does not hold it hostage to the Non-Greediness Principle, it is better to work with Broome’s earlier statement of the intuition, which does not prejudge the issue by definitional fiat.

19. The locus classicus is Chang (2002).

20. I thank Krister Bykvist and Luc Bovens for helpful conversations on these points.

21. This principle does not commit me to the claim that all populations of different sizes are incommensurate in value. Laying out a theory that specifies exactly when, and on what grounds, a larger population is better or worse than a smaller population is beyond the scope of this article. My concern here has been merely to show that, for a large number of situations and for a large range of levels of wellbeing, adding worthwhile lives to an existing population may be axiologically neutral. This is all that is needed to undermine the Argument from Additional Lives.

22. For an illuminating discussion of values that we respond to appropriately by promoting and values that we respond to appropriately by respecting and protecting their embodiments, see Scanlon (1998, Ch. 2).

23. For the distinction between intrinsic vs. extrinsic and instrumental vs. non-instrumental value, see Korsgaard (1996).

24. The claim that the human (and other) species have intrinsic value is defended at length in Rolston (1985). See also Bradley (2001).

25. So much at least seems true of things – like persons, objects, species, languages, etc. – which, given adequate care, can survive over extended periods of time. As Christine Korsgaard pointed out to me in conversation, the same concern for a thing’s survival isn’t necessarily part of responding appropriately to the value of essentially ephemeral things like sensory experiences or events (e.g. a concert). The relevant contrast in the appropriate attitudes may be roughly that between ‘cherishing’ and ‘savoring’.