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Philosopher of science Hasok Chang (University of Cambridge) joins Andrea Hiott to trace the through-line of his work — from Inventing Temperature (2004), through Is Water H₂O? (2012), to Realism for Realistic People (2022) — and to think together about what it means to treat knowledge as something we do rather than something we merely possess.

The conversation begins with why Inventing Temperature has quietly become an inspiration for neuroscientists: it shows how a felt quality (hot and cold) can become a trustworthy number (temperature) — not by discovering a pre-given fact, but through a messy, iterative, bootstrapping process of invention. From there, Chang and Hiott move through the ideas that organize his mature philosophy: epistemic iteration, operational coherence, active/activist realism, path dependence, conceptual engineering, and a pragmatist re-reading of truth that no longer leans on correspondence to an inaccessible reality.

A recurring theme: Chang describes each of his books as costing him “an article of faith” — first foundationalism, then monism, then the ideal of pure science — and how each loss opened onto a more dynamic, practice-based, and pluralist picture of knowing. Hiott connects these moves to her own navigational approach to mind and NAEC, where cognition is understood as a body’s coherent, aim-directed action in the world rather than the storage of static representations.

Full show notes here.

Hasok Chang is the Hans Rausing Professor of History and Philosophy of Science at the University of Cambridge. Trained first in physics (Caltech) and then in philosophy (Stanford), he is known for “integrated history and philosophy of science” and for what he calls complementary science — using historical and philosophical study to recover scientific questions that mainstream science has forgotten or foreclosed. His three main single-author books are Inventing Temperature (Oxford, 2004; winner of the 2006 Lakatos Award), Is Water H₂O? (Springer, 2012), and Realism for Realistic People (Cambridge, 2022). He is a founding figure of the Society for Philosophy of Science in Practice (SPSP) and the Committee for Integrated HPS.

Andrea Hiott is a philosopher and cognitive scientist developing the navigational approach to mind — the view that mind is “the body’s navigational action in all spaces of life, from the geographical to the emotional to the social to the virtual.” She hosts the Love & Philosophy (Beyond Dichotomy) podcast and Substack, and her work draws on hippocampal research, 4E cognition (embodied, embedded, extended, enactive), and the ecological tradition. Her book Holding Paradox: A Navigational Approach to Mind and Consciousness is forthcoming. Her recurring interests — holding apparent contradictions open, “way-making,” constellation/kaleidoscopic thinking, and moving beyond either/or — frame her questions to Chang throughout.

Chang’s three books at a glance

Book Year Central question “Article of faith” Chang says he lost Inventing Temperature 2004 How did scientists learn to measure temperature reliably without already having a trustworthy thermometer to check against? Foundationalism — the idea that knowledge rests on some ultimate, secure foundation (fundamental laws, or raw experience) Is Water H₂O? 2012 Was the consensus that water is H₂O actually forced by the evidence — and should science ever settle on a single account? Monism — the idea that there is one world, one truth, and one job for science: to find it Realism for Realistic People 2022 What would scientific realism look like if we started from practice and everyday life rather than from correspondence to an ultimate reality? The ideal of pure science — knowledge first, application second (he moves openly into pragmatism)

Key terms & concepts (glossary)

The definitions below are general but we're staying faithful to Chang’s own usage.

Epistemic iteration. Chang’s name for how inquiry actually makes progress: we don’t begin from a secure foundation, but knowingly start from an imperfect position and then use the results of inquiry to correct and refine that very starting point — a self-improving loop with no bedrock underneath. In Realism for Realistic People Chang invokes Peirce’s image that inquiry “is not standing on the bedrock of fact… It is walking upon a bog, and we can only say, this ground seems to hold for the present.” The aim is not coherence as such, but the ongoing improvement of coherence. (In the transcript Chang stresses that he first thought iteration solved only the narrow problem of validating measurement standards, then came to see it as a very general pattern of learning.)

Operational coherence. Roughly, “a harmonious fitting-together of the elements and aspects of an activity, which is conducive to the successful achievement of the aims of that activity.” It is Chang’s practice-based replacement for truth as correspondence: instead of asking whether a proposition matches reality, we ask whether an activity’s parts hang together well enough to reliably achieve its aim. Crucially, coherence is always defined relative to an aim — without a stated or assumed purpose, the word “coherence” has no meaning.

Epistemic activity. “A more-or-less coherent set of mental or physical operations that are intended to contribute to the production or improvement of knowledge in a particular way, in accordance with some discernible rules (though the rules may be unarticulated).” Examples: measuring, detecting, predicting, hypothesis-testing — but also mundane actions like lighting a match.

System of practice. A coherent, interacting set of epistemic activities carried out with a view to achieving certain overall aims. (This is the unit Chang argues can be legitimately plural: several incommensurable systems of practice can coexist productively within one discipline.)

Active knowledge / “knowing how.” Chang’s term (in Realism for Realistic People) for knowledge that resides in ability and action rather than in propositions — knowing how to do something rather than knowing that some statement is true. He argues proposition-based epistemology simply isn’t the right tool for evaluating methods, instruments, or institutions; for that we need to look at the coherence of what we do.

Active realism vs. activist realism (a terminology note). In Is Water H₂O? Chang introduced active realism: the view that realism shouldn’t be sitting back satisfied that we know a lot, but should be an attitude — even an “ideology” — committed to continually learning more and better about reality. In Realism for Realistic People he renamed it activist realism, to avoid confusion with his separate notion of active knowledge (someone might wrongly hear “active realism” as “any assured possession of active knowledge”). “Activist” better captures the ever-learning, never-shrinking commitment. (The two terms are easy to run together in conversation; Chang’s clarification here is the reference point for both.)

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#95 Inventing Temperature, Operational Coherence, Activist Realism and more with Cambridge philosopher of history and science Hasok Chang

love & philosophy

#95 Inventing Temperature, Operational Coherence, Activist Realism and more with Cambridge philosopher of history and science Hasok Chang