Scientists assert. They testify a lot. They do so when addressing collaborators (intrascientific testimony), peers, and publics (scientific expert testimony). These activities are thus a core element of scientific collaborative practices and central to science’s role in society. Scientific Testimony (2022) sets out to provide an epistemology of scientific testimony that appreciates its core functions. Scientific testimony does not reduce to scientists’ assertions, however. Rather, the book convincingly argues that science journalism (science reporting), too, is a species of public scientific testimony. What binds intrascientific and forms of public scientific testimony together is that assertions must be appropriately rooted in a science-specific kind of epistemic warrant: scientific justification. The epistemic norms governing the provision of such justification through testimony take center stage throughout the book.

Scientific Testimony builds on an impressive array of Mikkel Gerken’s previous publications in social epistemology, folk epistemology, and the specific topic at hand. It applies Gerken’s rigorous epistemological tools to tackle challenges that scientific testimony encounters both within science (intrascientific testimony) and when addressing nonscientific publics (public scientific testimony). These tools are Gerken’s purist invariantist contextualism: an antipragmatist, semantics-based epistemic contextualism. It assumes that epistemic warrant is invariant and unique, that is, fully determined across levels (from evidence to propositional warrant to doxastic warrant and through rejecting transmission views of epistemic warrant) and thus is nonpermissive.

Coherent with earlier writings, Gerken chooses not to “speak to the grand debate” (5; also 136, 182) on values in science. Yet in virtue of its subject, Scientific Testimony is arguably involved, as will become clear in this review. The book suggests answers to many of the same questions asked in the values and science debate and draws on a selection of its literature.

Thus, regardless of intention, Scientific Testimony’s usefulness to a philosophy of science audience will depend on the extent to which it can speak to the grand debates around science, values, and society, and I will evaluate the book’s main claims accordingly. This is why I will largely sidestep science reporting/journalism, but not without emphasizing that rooting scientific testimony in scientific justification rather than the testifier’s profession surely holds most fruitful insights for the epistemology of science journalism.

Part I lays out some groundwork. Testimony, we learn, is “an assertion that p, which is offered as ground for belief or acceptance that p on its basis” (46). Epistemic norms are truth-conducive idealizations that manifest as operative social norms. Scientific practice is guided by a complex set of operative norms, enforced through a Bicchieri-style sanction–reward system. Testimonial epistemic norms enjoy outstanding status within this system, facilitating division of cognitive labor and ultimately enabling science to pursue (approximate) truths.

Part II is dedicated to scientific justification and the epistemic norms for intrascientific testimony that heavily rely on it. Scientific justification is defined as a type of internalist warrant, that is, the epistemic reasons that a subject has (contrasting with externalist entitlements). It “generally involves a high degree of discursive justification” (95). Discursive justification consists of having articulable epistemic reasons for belief/acceptance, regardless of whether you articulate them (cf. 58). Scientific justification comes in degrees of “epistemic strength” (93): The more and/or better (articulatable) epistemic reasons you have for your belief/acceptance, the better.

Scientific justification is mostly “epistemically superior” (85) relative to nonscientific warrant. It thus epistemically supercharges scientific testimony.

Two epistemic norms guide communication in scientific collaborative practice. The epistemic norm of intrascientific testimony (NIST) guides testimony provision, and the responding epistemic norm of intrascientific uptake (NISU) guides testimony acceptance. Simplifying NIST and NISU’s highly technical wording: NIST (109) holds that for you to assert appropriately that p, it is necessary (but perhaps not also sufficient) that you have enough scientific justification for your belief/acceptance of p. And according to NISU (124), I have default entitlement to believe/accept your testimony and indeed should do so when I have strong and undefeated warrant to believe that you have enough such justification.

Propositional-level justification is not transmitted in NISU, but scientific justification allows me to tap into what reasons you have were you to articulate them. Because all participants in intrascientific testimony are scientists, recipients can typically utilize scientific justification.

Importantly, what counts as enough scientific justification in NIST and NISU is determined by the context of intrascientific communication (CISC) in which we are both embedded. CISC includes “urgency,” “stakes,” and social conventions (108) that set a “sliding threshold” (107). Two observations are essential here. First, CISC is intended to be purely epistemic, despite sounding pragmatic, and it seems every CISC generates a unique threshold we are bound to. Second, NIST is a sufficient-for-appropriate-assertion norm. The warrant you have for p (propositional) is invariably fixed by the evidence, and the warrant you have for believing p (doxastic) is invariably fixed by your propositional warrant. CISC merely requires that the warrant you do have contains enough scientific discursive justification to assert. CISC is strictly purist invariantist contextualism in pragmatist disguise.

The privileged status Gerken ascribes to intrascientific testimony ultimately rests on an observation: Communication (thus, testimony) saturates every aspect of scientific practice. Gerken convincingly argues that its epistemic impact is systemic and significant. To preserve and promote science’s epistemic force, activities of such prime importance need to be properly attended to.

But pace Gerken, testimony is not the only activity that fits this bill. Inquiry choices, small and big, saturate scientific practice, too. (Some say assertion is a choice.) Many of the trade-offs made in such choices have systemic, significant epistemic impact. Ceteris paribus, surely one should attend to those properly, too. And attending to them is exactly what the values in science debate has been doing. Post-Mertonian accounts of objectivity norms for scientific epistemic practice are sensitive to the need to responsibly manage such choices—including assertions—and potential value-use therein. This is to secure epistemic integrity not only in producing claims but also, and inseparably related, in asserting them with the reassurance that “I trust this, and you should too” (Douglas Reference Douglas2009, 116).

It seems, then, that an inherent tension underpins the book’s relationship with what participants in the values in science literature (including most defenders of value neutrality) agree to be epistemic problems worth attending to (cf. Holman and Wilholt Reference Holman and Wilholt2022); inquiry choices are one of them. By Gerken’s own criteria, such inquiry choices surely should equally matter. Yet the methodological constraints imposed by strict purist invariantism and nontransmission of warrant in testimony appear to not allow for the proper conceptualization or integration of them.

Black-boxing topics inherently related to value-judgements and how they bear on intrascientific testimony’s epistemic roles and obligations conceals their relevance for the book’s other goals, such as identifying systematic disruptions between public scientific testimony provision and “lay” uptake (part III), ameliorating idealized epistemic norms to mitigate such disruptions (also part III), and theorising in virtue of what science generates its privileged status in and for in an ideal democracy (part IV).

Part III identifies a series of systematic distortions in and failures of scientific testimonial uptake on the side of lay publics, mostly by drawing on literature from the science of science communication and folk epistemology. Some failures concern general cognitive biases and heuristics; some concern social identity, in-/out-group biases, and polarization effects; and some cluster around “folk” misconceptions of science.

The complexity of these issues means that mitigation, rather than elimination, is all one can hope for. The main mechanics NIST builds on, together with some useful norms of communicating epistemic strength (methodological limitations, uncertainty, expertise levels), Gerken argues, have good potential for such mitigation. Scientific Testimony thus ameliorates the epistemic norm of expert scientific testimony (NEST), which is similar to NIST, but with the relevant epistemic context being a broader “science communication context, SCC” (156).

Gerken provides useful empirical insights into how cognitive and social bias, bad actors, and hostile social environments get in the way of receiving information the public should have and ameliorates norms like NEST in response. But for appropriate amelioration or idealisation, it is certainly not enough to use any set of good empirical observations. Relevant/representative data arguably matters. And so, not including empirical data on policy advice, adequacy-for-purpose and mission-oriented research, or science services removes from the picture value-laden scientific activities crucial to understanding public trust in and trustworthiness of scientific testimony.

Part IV attempts a strictly purist invariantist reinterpretation of the familiar science and democracy literature: Ideal deliberative democracies need an informed public, and because of its epistemic superiority, scientific testimony itself, not the contents testified, is the “premier” (226) resource to satisfy that need. Democracy needs science’s testimony. Science sustains itself by providing it. Part IV also expands on society’s failure to provide a social environment that supports a lay public’s default uptake of scientific testimony and suggests an epistemic norm in response: appreciative deference, which incentivizes appreciation of scientific testimony’s epistemic superiority in pursuit of default trust. Democratic societies have a responsibility to enforce appreciative deference to ensure an informed public and avoid epistemic injustices.

Scientific Testimony ends with a brief discussion of distributive epistemic injustices that affect marginalized communities through a social environment that systematically denies marginalised persons the ability to appreciatively defer. This deprives them of the testimony necessary to either correct for a diverse and/or marginalized person’s misconception of themselves (254) or of the ability to use scientific justification to amplify their reports of experienced marginalization (255).

Appreciative deference arguably fits to counter such injustices and the important but selective themes of part III. But it also exposes the book’s methodological constraints most strikingly, for appreciative deference as an engineered norm makes sense only under the assumption that science is not the root of injustices—or at least not in ways worth mitigating through such norms. But the empirical and historical record clearly attests to systematic distributive epistemic injustice committed by producing either distorted approximate truths or falsehoods that served the oppressors and ignored, misconceived of, and/or directly harmed the oppressed. And it attests to testimonial epistemic injustices based on science’s systematic exclusion of marginalized voices from participating in and contributing to science. (Grasswick Reference Grasswick, Kidd, Medina and Pohlhaus2017) Epistemic injustices of being given access to listen to science are not the whole story.

Notably, neither invisible epistemic hands (33ff.) enabled by diverse epistemic perspectives by virtue of mere cognitive diversity (248ff.) nor a social epistemic environment of scientific collaboration guided by epistemic norms (36) internally self-corrected for these epistemic injustices. Very real hands—too often rendered invisible—did (and do) that by pressuring science and society for just inclusion and for being given the due right to speak and be heard in scientific collaboration.

Scientific epistemic practices just don’t always bend to our epistemological idealizations. And neither does aiming at approximate truth under the guise of epistemic neutrality/purity alone guarantee that scientific claims are born just or neutral. (Anderson Reference Anderson1995) Not reckoning with these empirical and theoretical insights hardly serves science’s epistemic integrity.

This is why attention in the debate about values in science shifted from oversimplified “purism–yes/no” questions toward recognizing the epistemic need for value management. But while Scientific Testimony can insightfully speak to some challenges that scientific testimony and its role in society pose, its framework seemingly struggles with integrating that epistemic need. Alas, by setting aside those challenges that don’t fit its specific purist invariantist lens, Scientific Testimony builds “the scientific edifice” (211ff.) on epistemological foundations hardly fit to bear the structure’s actual weight.