Ian Hacking

Ian Hacking (February 18, 1936 – May 10, 2023) was a Canadian philosopher of science who worked on probability, scientific realism, and the classification of people, and who introduced the ideas of "dynamic nominalism", "making up people", and the "looping effect" of human kinds¹. He held chairs at the University of Toronto and, from 2000, the Collège de France, and his honors included the Holberg Prize (2009) and the Balzan Prize (2014)². The Balzan citation described his work as an "original epistemological perspective centred on a version of scientific realism"³.

Life and career

Hacking was born in Vancouver, British Columbia, in 1936¹. He taught at the University of British Columbia from 1964 to 1969, with a year seconded to Makerere University College in Uganda (1968–69), then at Cambridge (1969–74) and Stanford (1975–82), before returning to the University of Toronto, where he taught from 1982 to 2004². Toronto appointed him University Professor in 1991, its highest honor². In 1991 he also delivered the Tarner Lectures at Trinity College, Cambridge⁵.

Collège de France. In 2000 Hacking became the first Anglophone elected to a permanent position at the Collège de France, holding the Chair in the Philosophy and History of Scientific Concepts until his retirement in 2006; he remained Professeur Honoraire of that chair and University Professor Emeritus at Toronto^{2 • 3}. In 2005 the French Le Nouvel Observateur named him one of the 25 greatest thinkers in the world².

He died on May 10, 2023, at a retirement home in Toronto, at 87, after years of declining health^{2 • 4}. A memorial essay in Common Knowledge records that his health had been declining since his wife, the philosopher Judith Baker, died in 2014¹⁰.

Representing and intervening: entity realism

Hacking's 1983 book Representing and Intervening is an introduction to the philosophy of natural science organized around scientific realism; its "Intervening" part presented the first sustained treatment of experimental science in many years and used experimentation to give a new direction to debates about realism¹¹.

His position within that debate is often summarized as entity realism: Hacking was anti-realist about theories but realist about theoretical entities, grounding the distinction in the claim that "[i]f you can spray electrons, then they are real" (Representing and Intervening, p. 23)⁹. The point is that manipulating an entity in experiment, as physicists do when they spray electrons in instruments, is a practical commitment to its existence that does not require believing the theories describing it. The Balzan Prize citation of 2014 recognized this stance as a "version of scientific realism" at the center of his epistemology³.

Historical ontology and styles of reasoning

Historical ontology. Historical Ontology (2002) collects 25 years of Hacking's writings on the intersections of philosophy and history⁶. Scholarship comparing the program with Michel Foucault's genealogy finds a structural difference: historical ontology acknowledges "language games" but does not treat them as constitutive of social reality, whereas genealogy treats "power games" as constitutive; in historical ontology, social reality is treated as a "non-existent entity", or quasi-reality, marked out as a purely linguistic entity¹². Other scholarship traces the Foucauldian lineage of Hacking's notions of "how we found out how to find out" to Foucault's Les Mots et les Choses (1966)¹³.

Styles of reasoning. In the 1980s Hacking, following the historian of science Alistair Crombie (1915–1996), claimed that there exist different scientific ways of knowing which emerged at specific points of human history, characterized by the notion of a "style of reasoning"¹⁴. The thesis was sketched in "Language, Truth and Reason" (1982) and "'Style' for historians and philosophers" (1992) and has never been fully developed into a comprehensive theory; Hacking used the label "The Styles Project" in his 2012 paper "'Language, Truth and Reason' thirty years later"¹⁴. For the project he experimented with titles such as "philosophical technology" and "philosophical anthropology"¹⁵. The thesis is usually positioned alongside Fleck's "thought style" (1935), Foucault's "episteme" (1966/1969), Kuhn's "paradigm" (1962), and Lakatos's research program (1978)¹⁴. Martin Kusch, a philosopher at the University of Vienna, published a critique of the styles project in Studies in History and Philosophy of Science in 2010, showing that the thesis has been an object of active debate rather than settled doctrine¹⁵.

Making up people: looping effects and human kinds

Hacking coined the slogan "making up people" to refer to how a new scientific classification may bring into being a new kind of person, conceived of and experienced as a way to be a person¹⁶. He described his nominalism as dynamic, interested in how names interact with the named, and traced the idea to Nietzsche's aphorism in The Gay Science⁷. Britannica summarizes the two halves: the influence of the label upon the self is "dynamic nominalism", and the endless cycle of label-person interaction, in which labels and people modify each other, is "the looping effect"¹.

How looping works. In Hacking's framework, interactive kinds are kinds whose members, in virtue of belonging to the kind, alter what it is to be that kind, and those changes feed back into the classification itself; the framework was developed across works from 1986 to 2007⁸. His own summary formula is that "classifying changes people, but the changed people cause classifications themselves to be redrawn"¹⁷. His paradigm examples include multiple personality disorder, autistic spectrum disorder, ADHD, bipolar disorder, child abuser, and psychopath⁸.

Multiple personality. The clearest documented case is the revival of the multiple personality disorder (MPD) diagnosis in North America in the 1980s, which led, over time, to an increase in the average number of alternate personalities reported by patients¹⁷. The disorder was renamed Dissociative Identity Disorder, and the symptoms evolved rather than merely being relabeled: patients are no longer expected to come with a roster of altogether distinct personalities, and they don't⁷. Hacking cited it as a "transient mental illness", transient not in the sense of affecting a single person for a while, but in the sense of existing only at a time and place, as analyzed in Mad Travelers¹⁶. In "Making Up People" he wrote that transient mental illnesses can best be looked at in terms of the ecological niches in which they can appear and thrive⁷. In "Kinds of People: Moving Targets" he classified fugue, "the fancy name for mad travelling", as a wholly closed, old example whose history is finished, all the facts being in¹⁸.

The DSM. In his 2013 review of DSM-5 in the London Review of Books, Hacking argued that the DSM is not a representation of the nature or reality of the varieties of mental illness, a criticism he called more radical than the claim that the book lacks "validity"¹⁹. He judged that something like the DSM remains essential for bureaucratic needs such as paying for treatment and assessing prevalence, but that the changes from DSM-IV to DSM-5 were not worth the prodigious labor involved¹⁹. He also criticized the DSM's premise that recognized varieties of mental illness should sort into tidy blocks the way plants and animals do¹⁹.

Partial retraction. In more recent work (2006, 2007), Hacking rejected the notion of interactive kinds because of reservations about the existence of natural kinds, while still accepting the existence of looping effects⁸.

Probability and chance

Hacking's two books on probability anchor his historical work. Cambridge University Press describes The Taming of Chance (1990) as showing how, by the late nineteenth century, it became possible to think of statistical patterns as explanatory in themselves, and how the idea of human nature was displaced by a model of normal people with laws of dispersion²⁰. The Emergence of Probability (1975, reissued 2006) is listed among his most groundbreaking books².

The science wars and social construction

Hacking's 1999 book The Social Construction of What? examines social construction and provides a balanced overview of the debates, sometimes called "the science wars", between scientists and constructionists⁶. The University of Toronto Archives finding aid records the book as a response to the philosophical debates surrounding the objectivity of scientific inquiry and theory⁵. His position between the camps is consistent with the Balzan framing of his epistemology as a "version of scientific realism"³.

References

1. Ian Hacking, Encyclopaedia Britannica
2. In memoriam: Ian Hacking (1936–2023), University of Toronto Department of Philosophy
3. Ian Hacking: Bio-bibliography, Balzan Prize Foundation
4. Ian Hacking, Eminent Philosopher of Science and Much Else, Dies at 87, The New York Times
5. Ian Hacking fonds, Finding Aid, University of Toronto Archives
6. Ian Hacking, The Canadian Encyclopedia
7. Ian Hacking, "Making Up People: clinical classifications", London Review of Books
8. Kinds behaving badly: intentional action and interactive kinds, Synthese
9. PhilArchive excerpt on Hacking's entity realism
10. Ian Hacking (1936–2023), Common Knowledge, Duke University Press
11. Representing and Intervening, Cambridge University Press catalogue
12. The Relations between Ian Hacking's Historical Ontology and Michel Foucault's Genealogy, Problemos
13. Number and Things: Foucauldian Contributions to the Work of Ian Hacking, Transversal
14. On Ian Hacking's Notion of Style of Reasoning, Erkenntnis
15. Kusch, "Hacking's historical epistemology: a critique of styles of reasoning", Studies in History and Philosophy of Science Part A
16. Ian Hacking, British Academy philosophical address
17. Concepts, Diagnosis and the History of Medicine: Historicising Ian Hacking and Munchausen Syndrome, Social History of Medicine
18. Ian Hacking, "Kinds of People: Moving Targets"
19. Ian Hacking, "Lost in the Forest: Who needs the DSM?", London Review of Books
20. The Taming of Chance, Cambridge University Press catalogue

Topic: Encyclopedia › Society and history › Philosophy, religion, and mythology › Philosophy › Philosophers and the profession › Philosopher categories and biographies › Individual philosopher biographies › Analytic philosophers and logicians

Initially written Oct 10, 2026 · Edited: Oct 11, 2026; Oct 15, 2026

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