Judith Jarvis Thomson (1929–2020) was a professor at the Massachusetts Institute of Technology (MIT) and one of the most rigorous voices in American analytic ethics during the second half of the twentieth century. Her work is distinguished by its meticulous analysis of concrete cases and its systematic use of thought experiments as testing devices for general moral principles. Educated at Columbia University and at Cambridge (UK), she devoted decades to the examination of rights, moral permissibility, causation, and responsibility — with particular attention to situations in which strong intuitions collide with otherwise coherent normative theories.
Thomson’s career can be read around two major poles. The first is the abortion debate: in “A Defense of Abortion” (1971), she proposed an argument radically different from the standard discussion, conceding arguendo that the fetus is a person from conception and maintaining that abortion is nonetheless morally permissible in many cases, on the grounds of the pregnant person’s rights over their own body. The second pole is the ethics of harmful action: together with Philippa Foot, Thomson made the “trolley problem” a canonical instrument of moral philosophy, developing it independently from 1976 onwards and revising her own conclusions in a late article. In her final decades she turned to metaethics and value theory, most fully in Goodness and Advice (2001).
Key Concepts
- The violinist argument (“A Defense of Abortion”, 1971): Thomson imagines a woman who wakes up connected to a famous but gravely ill violinist who depends on her circulatory system to survive. The conclusion is that even if the violinist has a right to life, the woman is not obliged to remain connected — because the right to life does not include the right to use another person’s body. The argument is deliberately agnostic about the moral status of the fetus: it grants full personhood in order to show that the right to abortion can be defended even on that assumption.
- The trolley problem: in “Killing, Letting Die, and the Trolley Problem” (1976) and in “The Trolley Problem” (1985), Thomson developed and systematised the thought experiment first introduced by Philippa Foot in 1967, exploring the moral distinctions between redirecting a runaway trolley — killing one to save five — and pushing a bystander off a bridge for the same purpose. The contrast between the two scenarios became the starting point for all subsequent literature on negative and positive duties.
- Killing versus letting die: Thomson examined the distinction between actively causing harm and failing to prevent it, questioning whether there is always a morally relevant difference between the two and wherein it consists.
- Revision in “Turning the Trolley” (2008): in a late article, Thomson changed her position and came to hold that redirecting the trolley — causing it to run over one person in order to save five — is also morally impermissible, since it constitutes a rights-violation comparable to the bridge variant. This reversal is a rare public display of a philosopher willing to revisit her own cardinal theses.
- Moral realism and value theory: in Goodness and Advice (2001), Thomson rejected subjectivist conceptions of goodness and examined the semantic and normative structure of evaluative predicates, defending a form of minimal moral realism.
Influenced by
- Philippa Foot — introduced the trolley problem in 1967; Thomson took it up and systematically expanded it
- H.L.A. Hart — theory of rights and legal and moral obligations
- The utilitarian tradition descending from John Stuart Mill, which Thomson implicitly challenges by privileging individual rights over aggregate welfare maximisation
Influenced
- Frances Kamm — developed principlism and thought experiments on harm and benefit directly from Thomson’s framework
- Joshua Greene — the neuroscience of morality and the trolley problem debate draw directly on the scenarios Thomson formulated
- The philosophical and legal debate on abortion, especially the literature on reproductive rights and bodily autonomy
- Applied ethics broadly: Thomson’s methodology — stress-testing principles with limiting cases — became a standard approach in normative ethics teaching and research
Works
- “A Defense of Abortion” (1971), in Philosophy & Public Affairs 1(1): 47–66 — the most cited article in the philosophical debate on abortion
- Acts and Other Events (1977) — theory of action, causation, and the individuation of events
- Rights, Restitution, and Risk: Essays in Moral Theory (1986) — collected essays on rights and responsibility
- “The Trolley Problem” (1985), in The Yale Law Journal 94(6): 1395–1415
- The Realm of Rights (1990) — systematic treatment of rights theory
- Moral Relativism and Moral Objectivity (1996) — co-authored with Gilbert Harman; debate between relativism and moral objectivism
- Goodness and Advice (2001) — metaethics and value theory
- “Turning the Trolley” (2008), in Philosophy & Public Affairs 36(4): 359–374 — revision of her positions on the trolley problem
See also
Philippa Foot, Frances Kamm, Joshua Greene, H.L.A. Hart, Bernard Williams