Ian MacDougall Hacking

1. Introduction

Ian MacDougall Hacking (1936–2023) was a Canadian philosopher and historian of science whose work is widely seen as reshaping late twentieth‑century debates about scientific realism, probability, and the classification of people. Trained in both mathematics and analytic philosophy, he became known for combining formal rigor with detailed historical and case‑study research.

Hacking’s philosophical contributions cluster around several interconnected themes. In philosophy of science, he advanced experimental realism, the view that reliable experimental manipulation of entities such as electrons or genes provides a distinctive ground for realism, independently of whether our overarching theories are true. Closely linked is his account of styles of scientific reasoning, historically evolving ways of arguing and evidencing—such as statistical, laboratory, or taxonomic styles—that structure what counts as rational scientific practice.

In the human sciences, Hacking developed an influential theory of human kinds, interactive kinds, and looping effects, analyzing how classifications of people—such as psychiatric diagnoses or risk categories—change the very individuals classified. This fed into his analysis of social construction, where he dissected talk of “constructed” phenomena into a family of more precise claims, applicable differently to, for example, quarks, child abuse, or multiple personality.

Hacking’s work crossed disciplinary boundaries, influencing philosophy, history and sociology of science, science and technology studies (STS), and philosophy of psychiatry. His writings are often used as exemplars of a practice‑based, historically informed approach to philosophy, in which laboratory techniques, bureaucratic procedures, and clinical routines are treated as philosophically central rather than merely illustrative.

2. Life and Historical Context

2.1 Biographical Outline

Ian Hacking was born on 18 February 1936 in Vancouver, British Columbia, and educated at the University of British Columbia before moving to Trinity College, Cambridge, where he studied mathematics and moral sciences. He completed his PhD in philosophy at Cambridge (1962–1964) under Casimir Lewy, with a dissertation on probability. Hacking subsequently held academic positions in North America and Europe, most prominently the Chair of Philosophy and History of Scientific Concepts at the Collège de France (1986–2006), a rare appointment for an anglophone philosopher. He died in Toronto on 10 May 2023.

2.2 Intellectual Milieu

Hacking’s career unfolded against the backdrop of major shifts in philosophy of science and the human sciences. The decline of logical positivism, the impact of Thomas Kuhn’s work on scientific revolutions, and the rise of historical and sociological approaches created an environment receptive to his historically oriented philosophy. At the same time, developments in statistics, epidemiology, psychiatry, and cognitive science furnished many of his case studies.

He engaged closely—but not uncritically—with analytic philosophy, French historical and epistemological traditions (notably Michel Foucault), and the emerging field of STS. The postwar growth of bureaucratic record‑keeping, social insurance, and psychiatric institutions formed much of the social backdrop for his analyses of probability, statistics, and classification.

2.3 Position Within Twentieth‑Century Thought

Commentators often place Hacking among post‑positivist philosophers of science who retained respect for scientific practice while rejecting unified, ahistorical accounts of method. Compared with contemporaries, he drew more heavily on archival history and concrete scientific practice, while also engaging continental thought more systematically than many Anglophone peers. This positioning helped make his work a bridge between analytic philosophy and historically grounded social studies of science.

3. Intellectual Development and Academic Career

3.1 Early Analytic and Probabilistic Phase

Hacking’s early intellectual development in the 1950s and 1960s was shaped by analytic philosophy and mathematical training. Under Casimir Lewy at Cambridge, he worked on probability and induction, culminating in The Logic of Statistical Inference (1967). In this period, his focus lay on the logical structure of statistical reasoning and the justification of inductive inference, with relatively little historical or sociological material.

3.2 Turn to History and Experimental Practice

In the 1970s, Hacking’s work took a decisively historical turn. Drawing on the new historiography of science associated with Kuhn and Foucault, he began to treat philosophical problems as historically situated. The Emergence of Probability (1975) and Why Does Language Matter to Philosophy? (1975) exemplify this shift, combining philosophical argument with detailed reconstruction of past practices. By the time of Representing and Intervening (1983), Hacking was emphasizing experiments, instruments, and laboratory routines as central to understanding realism, inaugurating his mature experimental realist position.

3.3 Styles of Reasoning and Human Kinds

From the mid‑1980s through the 1990s, especially after his election to the Collège de France, Hacking developed two major projects: styles of scientific reasoning and the analysis of human kinds. Works such as The Taming of Chance (1990) and Rewriting the Soul (1995) explored how probabilistic and memory‑based sciences generated new ways of knowing and new kinds of people. During this phase, his research increasingly intertwined philosophy of science, history, and social theory.

3.4 Later Reflections and Consolidation

In the late 1990s and 2000s, Hacking consolidated these strands. The Social Construction of What? (1999) systematized his views on construction and classification, while essays collected in Historical Ontology (2002) articulated his program for studying how kinds of things—and especially kinds of people—come to exist in particular historical settings. His later work continued to apply these tools to topics such as autism, childhood, and risk categories, while his teaching and lectures helped institutionalize practice‑based, historically sensitive philosophy of science in several countries.

4. Major Works and Their Themes

4.1 Overview Table

4.2 Early Works on Probability and Language

In The Logic of Statistical Inference, Hacking examined competing approaches to statistical inference, such as Bayesian and frequentist methods, treating them as rival logics of evidence. The Emergence of Probability extended this concern historically, tracing how notions of probability and statistical regularity arose in early modern Europe. Why Does Language Matter to Philosophy? reconstructed how twentieth‑century analytic philosophy’s “linguistic turn” shaped conceptions of meaning and truth.

4.3 Practice‑Oriented Philosophy of Science

Representing and Intervening is often regarded as Hacking’s most influential philosophy of science text. The first part surveys debates on scientific realism and representation; the second argues that experimental manipulation provides an independent route to realism, shifting focus from theories to laboratory practices.

4.4 Human Kinds, Construction, and Historical Ontology

In The Taming of Chance, Hacking portrayed statistical reasoning as a historically specific “style” that underpinned new forms of social administration. Rewriting the Soul used multiple personality and memory research to illustrate how classifications can “make up people.” The Social Construction of What? responded to widespread use of constructionist language by distinguishing different strengths and targets of construction claims. Historical Ontology gathered essays setting out his program for studying how kinds, especially human kinds, are historically constituted through practices, institutions, and technologies.

5. Core Ideas: Experimental Realism and Styles of Reasoning

5.1 Experimental Realism

Hacking’s experimental realism centers on the idea that manipulation provides a distinctive warrant for believing in unobservable entities. Rather than grounding realism solely in the truth or approximate truth of theories, he emphasized what experimenters can do with entities in the laboratory.

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“If you can spray them, then they are real.”

— Ian Hacking, Representing and Intervening (1983)

On this view, the ability to use electrons to draw tracks in cloud chambers, or to manipulate genes in bacterial cultures, supports realism about electrons or genes even if overarching theories remain contested. Proponents interpret this as decoupling realism from grand theoretical success and tying it to reliable intervention.

Critics have raised several concerns. Some argue that experimental success still relies on theoretical assumptions about what is being manipulated, so the separation from theory‑realism may be overstated. Others contend that experimental realism privileges laboratory contexts and may not translate straightforwardly to fields such as cosmology or macro‑evolution, where direct manipulation is limited.

5.2 Styles of Scientific Reasoning

Hacking’s notion of styles of scientific reasoning treats different scientific epochs and disciplines as operating within partially autonomous “styles”—for example, statistical, laboratory‑experimental, taxonomic, or model‑based styles. Each style incorporates characteristic ways of:

• Formulating questions
• Gathering and evaluating evidence
• Justifying conclusions

According to Hacking, once a style proves its capacity to generate stable knowledge—such as reproducible measurements or predictive regularities—it establishes its own standards of correctness. Some commentators see this as echoing French historical epistemology (e.g., Bachelard) and Kuhn’s paradigms, but with a finer‑grained focus on reasoning practices.

Supporters argue that this framework accommodates pluralism in scientific methods without lapsing into relativism, since each style can be assessed by its own historically developed criteria. Critics worry that the boundaries between styles are vague and that the account may underplay cross‑style integration and the role of overarching norms of rationality. Others question whether styles are explanatory concepts or mainly descriptive heuristics.

6. Human Kinds, Looping Effects, and Classification

6.1 Human Kinds and the Indifferent/Interactive Distinction

Hacking famously distinguished indifferent kinds from interactive kinds. Indifferent kinds, such as many physical or chemical categories, are not affected by how humans classify them. Interactive kinds, often human or social categories, involve people who can respond to being classified, so that the classification and the classified mutually influence each other.

Proponents hold that this distinction clarifies why social construction debates matter more for some categories than for others. Critics question the sharpness of the divide, noting that institutional practices around “indifferent” entities (e.g., nuclear materials) can also feed back into the world, and that some biological kinds may blur the line.

6.2 Looping Effects

Looping effects of human kinds describe feedback processes in which classifications of people alter their behavior, self‑understanding, and environments, leading to new phenomena and revised classifications.

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“Kinds of people are moving targets because our investigations interact with them, and change them.”

— Ian Hacking, “Making Up People,” London Review of Books (2006)

In Rewriting the Soul, Hacking applied this idea to multiple personality disorder, arguing that new diagnostic categories, therapeutic practices, and cultural narratives helped shape patients’ experiences and symptomatology. Similar analyses appear in his work on autism, childhood, and risk groups.

Supporters see looping effects as a powerful tool for analyzing the dynamics of psychiatric and social categories and for explaining historical variability in diagnoses. Some sociologists and philosophers, however, argue that the notion risks psychologizing what are primarily institutional or structural processes, or that it may understate material and biological constraints on how far classifications can reshape people. Others suggest that looping effects need clearer specification to be empirically testable.

6.3 Classification Practices

Across these discussions, Hacking treated classification as a central practice in the human sciences. He examined how categories emerge from statistics, clinical routines, legal codes, and bureaucratic needs. Alternative views emphasize, respectively, the role of power (as in Foucauldian analyses), economic interests, or phenomenological experience, sometimes criticizing Hacking for focusing more on epistemic and practical aspects of classification than on normative or political evaluation.

7. Philosophy of Probability, Statistics, and Chance

7.1 Historical Emergence of Probability

In The Emergence of Probability, Hacking argued that modern notions of probability and statistical inference arose in the seventeenth and eighteenth centuries from a convergence of gambling mathematics, legal reasoning, and early demographic statistics. He portrayed this as the birth of a new style of reasoning, not merely the refinement of an eternal concept of chance.

Proponents regard this historical account as showing that what now appears as a unified, abstract theory of probability is in fact a contingent product of specific social and intellectual developments. Some historians have proposed alternative genealogies, stressing, for example, scholastic discussions of chance or non‑European traditions, suggesting that Hacking’s story may be Eurocentric or overly focused on elite mathematical sources.

7.2 Competing Interpretations of Probability

Hacking engaged with the main interpretations of probability—frequentist, Bayesian, propensity, and logical. In The Logic of Statistical Inference, he analyzed how different approaches treat evidence and confirmation, and he continued to reflect on these issues through later essays. He sometimes described probability as a family of concepts and practices rather than a single unified notion.

Some readers see him as leaning toward an objective, frequency‑based view at certain points, while others emphasize his pluralistic stance, according to which different interpretations are appropriate for different contexts. Critics contend that this pluralism may leave unresolved normative questions about which interpretation scientists ought to adopt in cases of disagreement.

7.3 Statistics, Governance, and “The Taming of Chance”

In The Taming of Chance, Hacking traced how nineteenth‑century social statistics, life tables, and bureaucratic record‑keeping transformed perceptions of chance and necessity. Regularities in crime, suicide, and mortality rates led some thinkers to view societies as governed by “laws of large numbers,” reshaping concepts of responsibility and risk.

Supporters highlight this work as a major contribution to understanding how statistical practices underpin modern governance and social science. It has been influential in STS and historical sociology. Some philosophers note that Hacking’s emphasis on statistics as a style of reasoning may underplay the role of formal probability theory, while some historians argue that his narrative abstracts from local institutional differences.

8. Social Construction and the Human Sciences

8.1 Disentangling “Social Construction”

In The Social Construction of What?, Hacking analyzed the proliferation of claims that various phenomena are “socially constructed.” Rather than endorsing or rejecting constructionism wholesale, he proposed a taxonomy of constructionist claims, distinguishing, for example, between:

• Claims about the contingency of categories (they could have been otherwise)
• Claims about their dependence on social practices and institutions
• Claims about their potential to be changed or dismantled

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“Social construction is not a single doctrine but a family of theses, some trivial, some radical, some true, some false.”

— Ian Hacking, The Social Construction of What? (1999)

Proponents regard this as clarifying debates in philosophy, sociology, and cultural studies by showing that participants often talk past one another. Some constructionists, however, see his analysis as diluting the critical force of constructionism, while some realists argue that he remains too open to strong constructionist positions.

8.2 Human Sciences as a Prime Site of Construction

Hacking argued that the human sciences—especially psychiatry, psychology, and criminology—are particularly fertile ground for substantive social construction. Because many of their categories are interactive kinds, classifications and associated practices can significantly shape their referents. He used examples such as child abuse, homosexuality, multiple personality, and autism to examine how diagnostic categories emerge, stabilize, and sometimes decline.

Supporters in philosophy of psychiatry and STS see this as offering a nuanced middle ground between strict medical realism and radical anti‑psychiatry: psychiatric categories are neither mere fictions nor simply discovered natural kinds. Critics from different directions question whether Hacking adequately addresses issues of power, stigma, and inequality, or whether his focus on epistemic and classificatory dynamics leaves out ethical and political dimensions emphasized by critical theorists and service‑user movements.

8.3 Limits and Varieties of Construction

Hacking also insisted that constructionist claims apply very differently across domains. For some entities (e.g., quarks), social construction may be limited to the conceptual framework and institutions of inquiry; for others (e.g., child abuse categories), construction extends to the very existence and nature of the phenomena as recognized problems. Alternative views dispute where these boundaries lie, and some argue for stronger or weaker constructionist readings than Hacking was prepared to endorse.

9. Methodology: History, Case Studies, and Practice-Based Philosophy

9.1 Historical Ontology

Hacking described his broader methodological project as historical ontology: studying how kinds of things that “exist for us” come into being, stabilize, and sometimes disappear through historical practices.

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“There is no one logic of scientific inference, but a patchwork of styles of reasoning that have been invented, stabilized, and sometimes discarded.”

— Paraphrasing Hacking, Historical Ontology (2002)

Rather than asking only whether entities are real in an abstract sense, historical ontology examines how they become accessible, nameable, and actionable at particular times. Proponents see this as integrating metaphysics with detailed historical research; critics question whether ontological questions can be reduced to or fully captured by historical description.

9.2 Case Studies and Archival Work

Hacking’s writings rely heavily on case studies and archival sources: early probability treatises, nineteenth‑century statistical reports, psychiatric case notes, and laboratory manuals. He treated these not simply as illustrations but as primary data for philosophical analysis. This approach aligns him with practice‑oriented historians and sociologists of science.

Supporters argue that this method yields nuanced, context‑sensitive philosophical claims and guards against overly abstract theorizing. Some philosophers worry that the heavy reliance on selected case studies may limit the generality of his conclusions or make them vulnerable to revision as historical scholarship advances.

9.3 Practice-Based Philosophy of Science

Methodologically, Hacking emphasized practices—experiments, measurement routines, bureaucratic procedures—over purely theoretical structures. This practice‑based stance undergirds his experimental realism, styles of reasoning, and analyses of classification.

Alternative methodologies in philosophy of science prioritize formal modeling, logical reconstruction, or large‑scale sociological explanations. Critics of practice‑based approaches sometimes argue that they risk losing normative guidance about what counts as good science, or that they may slide into descriptive sociology. Defenders of Hacking’s approach reply that careful attention to practice can still support normative evaluation, though often in a local and historically specific way.

10. Impact on Philosophy, STS, and Psychiatry

10.1 Philosophy of Science

In philosophy of science, Hacking’s emphasis on experiments and styles of reasoning contributed to a shift away from theory‑centric models. Experimental realism has been taken up and modified by philosophers working on scientific instrumentation, simulation, and model‑based reasoning. His work on styles has influenced discussions of methodological pluralism and the structure of scientific rationality.

Some philosophers credit Hacking with helping bridge analytic philosophy and historically‑oriented approaches, while others maintain that his local, practice‑focused analyses leave unresolved broader questions about realism, explanation, or scientific progress.

10.2 Science and Technology Studies (STS) and History of Science

Hacking’s historically grounded accounts of probability, statistics, and classification have been widely cited in STS and historical sociology. The Taming of Chance and The Social Construction of What? in particular serve as reference points in studies of risk, governance, and quantification.

STS scholars have drawn on his concepts of looping effects and interactive kinds to analyze how technologies, databases, and classification systems shape identities and populations. Some STS authors, however, argue that Hacking’s work gives comparatively less attention to power relations, economic structures, and material infrastructures than more overtly political or Marxian analyses.

10.3 Philosophy of Psychiatry and Clinical Disciplines

In philosophy of psychiatry, Hacking’s analyses of multiple personality, autism, and other diagnoses have significantly influenced debates about the nature of mental disorders. His framework offers tools for understanding diagnostic change over time, the role of cultural scripts, and patient self‑interpretation.

Clinicians and psychiatric theorists have used his ideas to reflect on the construction and revision of diagnostic manuals such as the DSM. Some critics in psychiatry regard his emphasis on construction and looping effects as risking relativism about mental illness or underplaying neurobiological findings, while others see his work as compatible with a multifactorial, biopsychosocial understanding.

10.4 Interdisciplinary Reception

Hacking’s writings are taught across disciplines—philosophy, history, sociology, anthropology, and psychology. His influence is evident in the vocabulary of “making up people,” “interactive kinds,” and “looping effects,” now common in discussions of classification and identity. Responses vary: some adopt his categories directly; others use them as points of departure for alternative theories of social kinds or for more explicitly normative critiques of classification practices.

11. Legacy and Historical Significance

Hacking’s legacy is often discussed in terms of how he reoriented philosophy of science toward practice, history, and classification. Many commentators credit him with helping establish a style of inquiry in which detailed case studies and archival research are integral to philosophical argument, especially concerning probability, experimentation, and human kinds.

His concepts—experimental realism, styles of reasoning, interactive kinds, looping effects, and historical ontology—have entered the standard vocabulary of several fields. They continue to shape debates over scientific realism, the nature of psychiatric diagnosis, the governance of risk, and the status of social construction claims. Some scholars view him as a key figure in a broader movement that includes Kuhn, Foucault, and various STS thinkers, while also emphasizing his distinctive combination of analytic clarity and historical depth.

Assessments of his long‑term significance differ. Supporters argue that his work provides enduring tools for understanding the co‑production of knowledge and social reality, especially in the human sciences. Critics suggest that later developments in formal epistemology, causal modeling, or critical theory may overshadow aspects of his approach, or that his analyses need updating in light of digital data practices and genomics.

Nevertheless, Hacking is widely regarded as a central post‑positivist philosopher of science whose ideas continue to inform research programs on scientific practices and the making of kinds of people. His contributions are frequently invoked as touchstones in current efforts to integrate philosophical analysis with empirical studies of science and medicine.