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Engineering Life Expectancy and Non-identity Cases


In his paper “Eating Animals the Nice Way” McMahan (Daedalus 137(winter): 66–76, 2008) explores whether there are ways of routinely using non-human animals for human consumption that are morally acceptable. He dismisses a practice of benign animal husbandry, in which animals are killed prematurely and believes that a practice in which animals were engineered to drop down dead instantaneously at the same age would be equally wrong, even though it would not involve killing. Yet, McMahan considers his intuition that both practices are equally wrong with regard to our duties towards (or regarding) the involved animals hard to justify. This paper explains in more detail why this commonsensical intuition is indeed hard to justify and explores what it would take to justify it. It takes nothing less than a yet-to-be-specified plausible theory in population ethics and an account of welfare (or some related concept that gives us reasons for action) that deals in a plausible way with non-identity cases involving species- or breed-related differences in life expectancy.

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  1. McMahan, personal communication, November 2016.

  2. For a discussion of the replacement argument, see Lazari –Radek and Singer (2014, 374), Singer (2011, 94–123) and Višak (2013).

  3. For a recent argument against the view that existence can be better or worse for an individual than never existing, see Višak (2016).

  4. There are some interesting proposals, each of them with its own problems. See, for example, Meacham (2012) and Johann Frick, “Conditional Reasons and the Procreation Asymmetry,” unpublished manuscript.

  5. The larger absolute quantity of goods in the human’s future life is not the only reason for rescuing the human rather than the dog, according to McMahan. But we can ignore the other considerations here (See McMahan 2002).

  6. Kahane and Savulescu (2012) made a similar point about the relevance of statistical normalcy..

  7. Lin (2017) makes this point in an unpublished manuscript, available at, accessed on 14 February 2017.


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I thank Jeff McMahan for his comments on an earlier version of this paper. I also thank the participants of the Texas workshop on engineering and ethics, and in particular the editors of this special issue, for helpful suggestions.

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Correspondence to Tatjana Višak.

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Višak, T. Engineering Life Expectancy and Non-identity Cases. J Agric Environ Ethics 31, 281–293 (2018).

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  • Population ethics
  • Non-identity cases
  • Welfare
  • Fortune
  • Jeff McMahan
  • Animal engineering