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MIP does not save the impairment argument against abortion: a reply to Blackshaw and Hendricks
  1. Dustin Crummett
  1. Chair of Late Antique and Arabic Philosophy, Ludwig-Maximilians-Universitat Munchen, München 80539, Germany
  1. Correspondence to Dr Dustin Crummett, Ludwig-Maximilians-Universitat Munchen, München 80539, Germany; dustin.crummett{at}


Perry Hendricks’ original ‘impairment argument’ against abortion relied on ‘the impairment principle’ (TIP): ‘if it is immoral to impair an organism O to the nth degree, then, ceteris paribus, it is immoral to impair O to the n+1 degree.’ Since death is a bigger impairment than fetal alcohol syndrome (FAS), Hendricks reasons that, by TIP, if causing FAS is immoral, then, ceteris paribus, abortion is immoral. Several authors have argued that this conclusion is uninteresting, since the ceteris paribus clause is not satisfied in actual cases of abortion: women have reasons for wanting abortions which do not apply to drinking during pregnancy, so all else is not equal, and the conclusion is irrelevant to the morality of actual abortions. In a recent article in this journal, Hendricks and Bruce Blackshaw try to evade this criticism by replacing TIP with the ‘modified impairment principle’ (MIP): ‘if it is immoral to impair an organism O to the nth degree for reason R, then, provided R continues to hold (or is present), it is immoral to impair O to the n+1 degree.’ MIP allows us to derive the ultima facie wrongness of abortion (not just its ceteris paribus wrongness) because MIP lacks a ceteris paribus clause. But I argue that this lack also renders MIP false: MIP faces counterexamples and implausibly produces genuine moral dilemmas. Since the moral principle on which it relies is false, the modified impairment argument fails. I close by considering what a principle would need to do for the impairment argument to succeed.

  • abortion
  • applied and professional ethics
  • ethics
  • political philosophy
  • public health ethics

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  • Contributors I am the sole author of the paper.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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