Experimental philosophy, broadly understood, is the empirical study of empirical questions that are philosophically significant. More narrowly understood, it is the empirical study of philosophically significant concepts, such as the concepts of knowledge or causation, and judgments, such as the so-called Gettier intuition (the judgment that one does not acquire knowledge if one forms a true judgment by luck). While the methods of experimental philosophy were originally drawn from experimental psychology, experimental philosophers have recently broadened their toolbox by including qualitative interviews, ethnographic methods, text analysis, and citation analysis. The scope of experimental philosophy has also been broadened in recent years, and it has transformed itself into a thriving interdisciplinary endeavor.

History

Philosophers have engaged in scientific and sometimes empirical inquiry for centuries: Aristotle reported biological observations (Lennox, 2001), Descartes’s The World exposed his mechanistic physics (Descartes, 1998), Kant wrote treaties about geography and cosmology (Schönfeld & Thompson, 2023), and James was a psychologist and philosopher (James, 2007). Although their philosophical ideas were rarely disconnected from their scientific research, it is, however, not always clear whether philosophers viewed their scientific work as means to answer philosophical questions (Sytsma & Livengood, 2019).

The first attempts to conduct explicitly empirical work to address philosophical questions can be traced to Naess’s (1938a, 1938b) empirical study of the concept of truth (for historical discussion, see Barnard & Ulatowski, 2016) and to Brandt’s (1954) anthropological research on moral judgments among the Hopi. Brandt’s goal was to examine, by ethnographic means, whether variation in moral judgment (e.g., the judgment that it is not morally wrong to torture animals for fun) could be explained by appealing to differences in empirical beliefs (e.g., whether or not animals feel pain); his empirical interest was prompted by the so-called “argument from disagreement” in meta-ethics: If moral judgments vary without variation in empirical beliefs, then moral judgments are implausibly viewed as describing an objective moral reality (Doris et al., 2020).

Despite these precursors, experimental philosophy emerged only in the early 2000s as a self-aware research program in philosophy, with a series of influential articles (e.g., Knobe, 2003; Machery et al., 2004; Nahmias et al., 2005; Weinberg et al., 2001) and edited collections (e.g., Knobe & Nichols, 2008). Experimental philosophy was originally a topic of heated controversy in philosophy, since it challenged the dominant methods in philosophy, which left no room for empirical work (Williamson, 2007). After a decade of controversy, experimental philosophy has gone mainstream within the field, with articles on a broad range of topics, using different methods, published in prominent philosophy outlets.

Core concepts

It is common to distinguish the positive and negative programs of experimental philosophy. The negative program aims at undermining some dominant methods and views in philosophy, such as the use of thought experiments; the positive program aims at understanding philosophically significant concepts as well as the psychology underlying philosophically significant judgments.

Experimental philosophy has been traditionally presented as studying philosophical intuitions. It is, however, controversial what intuitions are in philosophy. Some propose that intuitions are a distinct kind of mental states, akin to perceptual states (Chudnoff, 2013); others identify them with (typically quick and unreflective) judgments that are not derived from philosophical theories, yet others, in a deflationary spirit, to any judgment applying a philosophical concept to a particular situation described by a short text (Williamson, 2007). Some also deny that philosophy appeals to intuitions (Cappelen, 2012).

Experimental philosophers working in the negative program often argue that their empirical findings challenge the justification or warrant of philosophical intuitions or judgments (e.g., the Gettier intuition). They claim that these judgments are easily influenced by biases (e.g., they manifest order effects) or that they are parochial, varying across demographic groups.

Questions, controversies, and new developments

The first question is metaphilosophical: To what extent does experimental philosophy challenge the way philosophy is conducted? Some philosophers have argued that experimental philosophers’ main findings challenge the theoretical ambitions of philosophers (Machery, 2017), others that they are mostly irrelevant (Cappelen, 2012; Deutsch, 2015).

A question that is both empirical and metaphilosophical is about the nature of expertise in philosophy: Do philosophers’ judgments and concepts differ from lay people’s? Are the former immune to the biases that influence the latter? Although research is still on-going, an impressive body of evidence suggests that philosophers and lay people’s concepts and judgments are more similar than one might have thought (Schwitzgebel & Cushman, 2015).

Other questions are more squarely empirical. Experimental philosophers disagree about the extent to which philosophically significant concepts and judgments vary, e.g., across cultures or social-economic status (for contrasting views, see Knobe, 2019; Stich & Machery, 2023).

Perhaps the most noteworthy development in experimental philosophy is the appeal to a more diverse set of tools and methods (e.g., reaction time measures, eye-tracking, qualitative interviews, ethnography; see Fischer & Curtis, 2019). Particularly noteworthy is the use of text-analytic tools to study the use of concepts in an ecologically valid manner (e.g., Sytsma & Reuter, 2017).

Finally, the replicability of experimental philosophy has been examined and appears to be substantial (Cova et al., 2021) [see Open Science].

Broader connections

Experimental philosophy has become a rich interdisciplinary research project that is intertwined with most areas of cognitive science, including anthropology, cultural psychology, moral psychology (e.g., Buckwalter & Turri, 2015), formal modeling (e.g., Icard et al., 2015), linguistics, and the cognitive science of religion.

Experimental philosophers’ work is influencing scientific research, particularly psychology, but also law, linguistics, and anthropology. Scientific journals regularly publish interdisciplinary work inspired by experimental philosophy, such as articles on the lay concepts of belief, religious credence, lying, consent, moral judgments about moral luck or about the reference of proper names, the relation between judgments about what is possible and moral judgments, causal judgments, or the nature of lexical statutory meaning, to give just a few examples.

Experimental Philosophy

History

Core concepts

Questions, controversies, and new developments

Broader connections

Further reading