John Turri

philosophical science


“Could we obtain a distinct and full history of all that hath passed in the mind of a child, from the beginning of life and sensation, till it grows up to the use of reason, this would be a treasure of natural history, which would probably give more light into the human faculties, than all the systems of philosophers about them since the beginning of the world.”
— Thomas Reid


Philosophy does not have a distinctive methodology. Philosophers make progress by drawing on the findings and methodologies of other disciplines, always on the lookout for tensions and unarticulated assumptions and often with an eye toward the big picture. I practice philosophy as a form of inquiry continuous with science. My work combines conceptual clarity and behavioral experimentation, is deeply informed by the history of philosophy, and is sensitive to findings from the cognitive, social, and life sciences.


Philosophy doesn't have a distinctive methodology, but it does ask distinctive questions and encourages a healthy dichotomy of mind. On the one hand, philosophy encourages you to pursue the big picture — to ask the big and deep questions and seek out their connections. On the other hand, philosophy encourages you to pursue the small picture — to be mindful of inconspicuous and ordinary details and seek out their consequences. I believe this combination of contrary intellectual impulses helps to distinguish the philosophical mindset and makes philosophy both exasperating and exhilarating, often at the same time.

Here are some topics and questions I work on, often in collaboration with others. In almost every case, I'm interested in developmental, social, cultural, and comparative dimensions to the questions. That is, I'm also interested in how the relevant concepts, categories, and practices vary across the human lifespan, different social settings, human cultures, and different species. For more details, visit the Philosophical Science Lab.


What is knowledge? How does knowledge relate to action, evidence, doubt, and belief? Must knowledge be reliably produced? Is the concept of knowledge a human universal?


What is the norm of assertion? That is, when should you make an assertion? What distinguishes assertion from guessing or guaranteeing? What, if anything, distinguishes the human practice from assertion from the signaling behavior found in other species?


What is belief? When should you form a belief? How does belief relate to action, evidence, doubt, and knowledge? Are there different kinds of belief?


What is it to lie? Can you lie by saying something true? Does lying require you to know that you're saying something false? Does lying require you to intend to deceive your audience? Can you lie to yourself? Do non-human animals lie?


How does responsibility relate to blame? How does it relate to the ability to do otherwise?


What is an excuse? How does excuse relate to blame, rules, consequences, and emotions? How does being excused affect us? How should it affect us?


What is the purpose of blame? How does it relate to excuse, rules, consequences, and emotions? How does being blamed affect us? How should it affect us?


What is luck? How does it relate to ability, responsibility, and chance? How should it relate to our practices of excusing, blaming, and crediting people for outcomes?

personal identity

What criteria do we use to identify and re-identify indivuals across time and space? Are these criteria coherent? How do our criteria differ from those used by other social species?


If there is a chance that something is false, how does that affect decisions about how to act or what is known? Are there qualitatively different forms of uncertainty?

“Origin of man now proved. He who understands baboon would do more towards metaphysics than Locke.”
— Charles Darwin

Select publications

(For a complete publication list, see here.)


articles + chapters

The truth about lying

Turri, A., & Turri, J. (2015). The truth about lying. Cognition.

keywords: lying | deception | social cognition

The standard view in social science and philosophy is that lying does not require the liar’s assertion to be false, only that the liar believes it to be false. We conducted three experiments to test whether lying requires falsity. Overall, the results suggest that it does. We discuss some implications for social scientists working on social judgments, research on lie detection, and public moral discourse.

Knowledge and luck

Turri, J., Buckwalter, W., & Blouw, P. (2015). Knowledge and luck. Psychonomic bulletin & review.

keywords: knowledge attribution | luck | social cognition

Nearly all success is due to some mix of ability and luck. But some successes we attribute to the agent’s ability, whereas others we attribute to luck. To better understand the criteria distinguishing credit from luck, we conducted a series of four studies on knowledge attributions. Knowledge is an achievement that involves reaching the truth. But many factors affecting the truth are beyond our control and reaching the truth is often partly due to luck. Which sorts of luck are compatible with knowledge? We find that knowledge attributions are highly sensitive to lucky events that change the explanation for why a belief is true. By contrast, knowledge attributions are surprisingly insensitive to lucky events that threaten but ultimately fail to change the explanation for why a belief is true. These results shed light on our concept of knowledge, help explain apparent inconsistencies in prior work on knowledge attributions, and constitute progress toward a general understanding of the relation between success and luck.

For the greater goods? Ownership rights and utilitarian moral judgment

Millar, J.C., Turri, J., & Friedman, O. (2014). For the greater goods? Ownership rights and utilitarian moral judgment. Cognition.

keywords: moral psychology | ownership | consequentialism

People often judge it unacceptable to directly harm a person, even when this is necessary to produce an overall positive outcome, such as saving five other lives. We demonstrate that similar judgments arise when people consider damage to owned objects. In two experiments, participants considered dilemmas where saving five inanimate objects required destroying one. Participants judged this unacceptable when it required violating another’s ownership rights, but not otherwise. They also judged that sacrificing another’s object was less acceptable as a means than as a side-effect; judgments did not depend on whether property damage involved personal force. These findings inform theories of moral decision-making. They show that utilitarian judgment can be decreased without physical harm to persons, and without personal force. The findings also show that the distinction between means and side-effects influences the acceptability of damaging objects, and that ownership impacts utilitarian moral judgment.

Excuse validation: a study in rule-breaking

Turri, J., & Blouw, P. (2014). Excuse validation: a study in rule-breaking. Philosophical studies.

keywords: blame | excuses | rules | speech acts | moral psychology

Can judging that an agent blamelessly broke a rule lead us to claim, paradoxically, that no rule was broken at all? Surprisingly, it can. Across seven experiments, we document and explain the phenomenon of excuse validation. We found when an agent blamelessly breaks a rule, it significantly distorts people’s description of the agent’s conduct. Roughly half of people deny that a rule was broken. The results suggest that people engage in excuse validation in order to avoid indirectly blaming others for blameless transgressions. Excuse validation has implications for recent debates in normative ethics, epistemology and the philosophy of language. These debates have featured thought experiments perfectly designed to trigger excuse validation, inhibiting progress in these areas.

Is probabilistic evidence a source of knowledge?

Friedman, O., & Turri, J. (2015). Is probabilistic evidence a source of knowledge? Cognitive science.

keywords: knowledge | folk epistemology | probabilistic evidence | theory of mind

We report a series of experiments examining whether people ascribe knowledge for true beliefs based on probabilistic evidence. Participants were less likely to ascribe knowledge for beliefs based on probabilistic evidence than for beliefs based on perceptual evidence (Experiments 1 and 2A) or testimony providing causal information (Experiment 2B). Denial of knowledge for beliefs based on probabilistic evidence did not arise because participants viewed such beliefs as unjustified, nor because such beliefs leave open the possibility of error. These findings rule out traditional philosophical accounts for why probabilistic evidence does not produce knowledge. The experiments instead suggest that people deny knowledge because they distrust drawing conclusions about an individual based on reasoning about the population to which it belong, a tendency previously identified by “judgment and decision making” researchers. Consistent with this, participants were more willing to ascribe knowledge for beliefs based on probabilistic evidence that is specific to a particular case (Experiments 3A and 3B).

When words speak louder than actions

Rose, D., Buckwalter, W., & Turri, J. (in press). When words speak louder than actions: delusion, belief and the power of assertion. Australasian journal of philosophy.

keywords: delusion | belief | folk psychology | assertion

People suffering from severe monothematic delusions, such as Capgras, Fregoli or Cotard patients, regularly assert extraordinary and unlikely things. For example, some say that their loved ones have been replaced by impostors. A popular view in philosophy and cognitive science is that such monothematic delusions aren’t beliefs because they don’t guide behavior and affect in the way that beliefs do. Or, if they are beliefs, they are somehow anomalous, atypical, or marginal beliefs. We present evidence from five studies that folk psychology unambiguously views monothematic delusions as stereotypical beliefs. This calls into question widespread assumptions in the professional literature about belief’s stereotypical functional profile. We also show that folk psychology views delusional patients as holding contradictory beliefs. And we also show that frequent assertion is a powerful cue to belief-ascription, more powerful than even a robust and consistent track record of non-verbal behavior.

Skeptical appeal: the source-content bias

Turri, J. (2014). Skeptical appeal: the source-content bias. Cognitive science.

keywords: biases | skepticism | knowledge attributions | cognitive evaluation | inference | perception

Radical skepticism is the view that we know nothing, or at least next to nothing. Nearly no one actually believes that skepticism is true. Yet it has remained a serious topic of discussion for millennia and it looms large in popular culture. What explains its persistent and widespread appeal? How does the skeptic get us to doubt what we ordinarily take ourselves to know? I present evidence from two experiments that classic skeptical arguments gain potency from an interaction between two factors. First, people evaluate inferential belief more harshly than perceptual belief. Second, people evaluate inferential belief more harshly when its content is negative (i.e. that something is not the case) than when it’s positive (i.e. that something is the case). It just so happens that potent skeptical arguments tend to focus our attention on negative inferential beliefs, and we are especially prone to doubt that such beliefs count as knowledge. That is, our cognitive evaluations are biased against this specific combination of source and content. The skeptic sows seeds of doubt by exploiting this feature of our psychology

Belief through thick and thin

Buckwalter, W., Rose, D., & Turri, J. (in press). Belief through thick and thin. Noûs.

keywords: belief | knowledge | entailment thesis | folk psychology

 We distinguish between two categories of belief — thin belief and thick belief — and provide evidence that they approximate genuinely distinct categories within folk psychology. We use the distinction to make informative predictions about how laypeople view the relationship between knowledge and belief. More specifically, we show that if the distinction is genuine, then we can make sense of otherwise extremely puzzling recent experimental findings on the entailment thesis (i.e. the widely held philosophical thesis that knowledge entails belief). We also suggest that the distinction can be applied to debates in the philosophy of mind and metaethics.

Winners and losers in the folk epistemology of lotteries

Turri, J., & Friedman, O. (2014). Winners and losers in the folk epistemology of lotteries. In J. R. Beebe (Ed.), Advances in experimental epistemology. Continuum.

keywords: prediction | expectations | norms | speech acts

Two assumptions anchor most contemporary discussions of knowledge in cases of (large, fair, single-winner) lotteries. First, based on the long odds alone, you don’t know that your ticket lost. Second, based on watching a news report of the winning numbers, you do know that your ticket lost. Moreover, it is often treated as an uncontroversial datum that this is how most people view matters. Explaining why people hold this combination of attitudes is then treated as a criterion for an acceptable theory of knowledge and knowledge attributions. But do people actually hold the views they’re assumed to hold? We did the necessary empirical work to find out. We studied people’s reactions to lottery cases and discovered that they respond as predicted. We report those results here. We also evaluate three previous explanations for why people deny knowledge in lottery cases; none of them seems to work. Finally, we present evidence for a new explanation for why some people deny knowledge in lottery cases. We suggest that they deny knowledge in lottery cases due to formulaic expression.

Telling, showing and knowing: a unified theory of pedagogical norms

Buckwalter, W., & Turri, J. (2014). Telling, showing and knowing: a unified theory of pedagogical norms. Analysis.

keywords: knowledge | instruction | demonstration | assertion | culture | norms

Pedagogy is a pillar of human culture and society. Telling each other information and showing each other how to do things comes naturally to us. A strong case has been made that declarative knowledge is the norm of assertion, which is our primary way of telling others information. This paper presents an analogous case for the hypothesis that procedural knowledge is the norm of instructional demonstration, which is a primary way of showing others how to do things. Knowledge is the norm of telling and showing. It is the prime pedagogical principle.

Unreliable knowledge

Turri, J. (2015). Unreliable knowledge. Philosophy and Phenomenological Research, 90(3), 529–545,

keywords: knowledge | reliabilism | ability | achievement | explanatory inference

There is a virtual consensus in contemporary epistemology that knowledge must be reliably produced. Everyone, it seems, is a reliabilist about knowledge in that sense. I present and defend two arguments that unreliable knowledge is possible. My first argument proceeds from an observation about the nature of achievements, namely, that achievements can proceed from unreliable abilities. My second argument proceeds from an observation about the epistemic efficacy of explanatory inference, namely, that inference to the best explanation seems to produce knowledge, even if it isn’t reliable. I also propose a successor to standard versions of reliabilism, which I call “ecumenical reliabilism.” Ecumenical reliabilism is consistent with unreliably produced knowledge and helps explain why unreliably produced knowledge is possible.

The test of truth

Turri, J. (2013). The test of truth: An experimental investigation of the norm of assertion. Cognition, 129(2), 279–291.

keywords: assertion | norms | truth | knowledge | speech acts | blame | excuses | rules | intuitions

Assertion is fundamental to our lives as social and cognitive beings. Philosophers have recently built an impressive case that the norm of assertion is factive. That is, you should make an assertion only if it is true. Thus far the case for a factive norm of assertion been based on observational data. This paper adds experimental evidence in favor of a factive norm from six studies. In these studies, an assertion’s truth value dramatically affects whether people think it should be made. Whereas nearly everyone agreed that a true assertion supported by good evidence should be made, most people judged that a false assertion supported by good evidence should not be made. The studies also suggest that people are consciously aware of criteria that guide their evaluation of assertions. Evidence is also presented that some intuitive support for a non-factive norm of assertion comes from a surprising tendency people have to misdescribe cases of blameless rule-breaking as cases where no rule is broken.

Epistemic situationism and cognitive ability

Turri, J. (in press). Epistemic situationism and cognitive ability. In M. Alfano & A. Fairweather (Eds.), Epistemic situationism. Oxford: Oxford University Press.

keywords: knowledge | ability | reliability | abilism | situationism | social psychology

Leading virtue epistemologists defend the view that knowledge must proceed from intellectual virtue and they understand virtues either as refined character traits cultivated by the agent over time through deliberate effort, or as reliable cognitive abilities. Philosophical situationists argue that results from empirical psychology should make us doubt that we have either sort of epistemic virtue, thereby discrediting virtue epistemology’s empirical adequacy. I evaluate this situationist challenge and outline a successor to virtue epistemology: abilism. Abilism delivers all the main benefits of virtue epistemology and is as empirically adequate as any theory in philosophy or the social sciences could hope to be.

From virtue epistemology to abilism: theoretical and empirical developments

Turri, J. (2015). From virtue epistemology to abilism: theoretical and empirical developments. To appear in a volume on The Character Project, Ed. Christian Miller, Oxford University Press.

keywords: knowledge | ability | reliability | belief | truth | luck | causal cognition | folk metaphysics

I review several theoretical and empirical developments relevant to assessing contemporary virtue epistemology’s theory of knowledge. What emerges is a leaner theory of knowledge that is more empirically adequate, better captures the ordinary conception of knowledge, and is ripe for cross-fertilization with cognitive science. I call this view abilism. Along the way I identify several topics for future research.

A conspicuous art

Turri, J. (2013). A conspicuous art: putting Gettier to the test. Philosophers’ Imprint, 13(10), 1–16.

keywords: knoweldge | methodology | intuitions | folk epistemology

Professional philosophers say it’s obvious that a Gettier subject does not know. But experimental philosophers and psychologists have argued that laypeople and non-Westerners view Gettier subjects very differently, based on experiments where laypeople tend to ascribe knowledge to Gettier subjects. I argue that when effectively probed, laypeople and non-Westerners agree that Gettier subjects do not know.

Reid on the priority of natural language

Turri, J. (2014). Reid on the priority of natural language. Canadian Journal of Philosophy.

keywords: Thomas Reid | Noam Chomsky | artificial signs | natural signs | artificial language | natural language

Thomas Reid distinguished between natural and artificial language and argued that natural language has a very specific sort of priority over artificial language. This paper critically interprets Reid’s discussion, extracts a Reidian explanatory argument for the priority of natural language, and places Reid’s thought in the broad tradition of Cartesian linguistics.


My research has been funded by the Social Sciences and Humanities Research Council of Canada, the Ontario Ministry of Economic Development and Innovation, the Templeton Foundation, the British Academy and Association of Commonwealth Universities, the National Endowment for the Humanities, and the Canada Research Chairs program.