1. Introduction
The philosophical interest in deep disagreements began with Robert Fogelin’s famous article, “The Logic of Deep Disagreements,” (Fogelin Reference Fogelin1985) in which he argues that there is a type of disagreement that is rationally irresolvable. Since the publication of the paper, a growing body of literature has primarily focused on discussing this skeptical thesis. However, as any person interested in the topic quickly learns, there is not a single concept of deep disagreement shared by all (or the majority) of the scholars who research the topic. Strikingly, the ambivalence seems to already be present in the very paper that initiates this research field. In Fogelin’s work, there are at least two different characterizations of the nature of the phenomenon, which may appear to be not immediately reconcilable. According to one characterization of the phenomenon, deep disagreements arise from the parties being committed to inconsistent propositions of a certain kind: “we get a deep disagreement when the argument is generated by a clash of framework propositions” (1985, 5). According to a second characterization, however, deep disagreements do not consist of a clash of particular propositions but rather between systems of propositions: “when we inquire into the source of a deep disagreement, we do not simply find isolated propositions (“The fetus is a person.”), but instead a whole system of mutually supporting propositions (…)” (1985, 6).Footnote 1
Subsequent scholarship has provided additional definitions that are prima facie inconsistent with the two just mentioned. A portion of recent research on the topic has been drawn to the idea, originally proposed by Michael Lynch (Reference Lynch, Haddock, Millar and Pritchard2010), that deep disagreements in epistemology occur when agents rely on different “fundamental epistemic principles” – principles that cannot be justified in a non-circular way. Scholars influenced by Wittgenstein’s views on the structure of rational evaluation, as expressed in On Certainty, tend to interpret deep disagreements as scenarios where two opposing sides confront each other with differing “hinge commitments” (Pritchard Reference Pritchard2018; Johnson Reference Johnson2022). Some scholars argue that deep disagreements arise from a conflict of the “underlying normative commitments” of the disagreeing parties (de Ridder Reference de Ridder, Edenberg and Hannon2021), while others suggest they involve conflicting understandings of one or more concepts (Shields Reference Shields2018) or conflicting “systems of mutually supporting propositions” (Lavorerio Reference Lavorerio2021a). Still others maintain that deep disagreement occurs when no “Archimedean meta-norm” is available (Carter Reference Carter2016).
The proliferation of prima facie inconsistent accounts of the nature of deep disagreement might be seen as a handicap for this research field due to the dispersion of research efforts and, more seriously, the risk of equivocations when discussing central questions such as whether deep disagreements are rationally resolvable. It might seem that research on the topic should strive for a single precise and shared concept. This conviction has recently prompted some scholars to seek ways of arbitrating between these varying conceptions (Ranalli Reference Ranalli2021; Ranalli and Lagewaard Reference Ranalli and Lagewaard2022a, Reference Ranalli and Lagewaard2022b). Drawing on Ranalli (Reference Ranalli2021), I refer to this endeavor as the metaphysical program. Its aim is to provide criteria for deciding what is the best way of thinking about the nature of deep disagreement.
One proposal within the metaphysical program adopts descriptive analysis as a model. As a rough characterization, descriptive analysis is the philosophical endeavor that seeks to describe the meaning that a concept holds within a particular community of users (for example, users of ordinary language). Well-known examples include the analysis of knowledge as justified true belief and the analysis of truth as correspondence. As they are typically understood, they aim to capture the meaning that “knowledge” and “truth” have in non-philosophical contexts. The method to establish whether a proposal of descriptive analysis is correct and to arbitrate between different proposals of the same concept is the so-called “method of cases”: Given a target concept x, a correct analysis of x must accommodate all instances (real or hypothetical) that intuitively qualify as “x,” while excluding those that do not. If a case (real or imaginary) is presented that intuitively satisfies the analysans but not the analysandum, or vice versa, the analysis is proven to be incorrect.Footnote 2 In essence, a correct analysis is one that can align with our intuitions about real and possible cases. Edmund Gettier employed this method to challenge the traditional analysis of “knowledge.” In his 1963 article “Is Justified True Belief Knowledge?,” he presented two hypothetical scenarios in which a person is justified in believing a true proposition, but intuitively does not know it.
If philosophical concepts of deep disagreement are to be conceived as descriptive analyses of the lay conceptFootnote 3 , the method of cases would also be an appropriate strategy to arbitrate between them. To demonstrate the inadequacy of a proposal, it would be sufficient to present an instance (real or imaginary) of disagreement that is intuitively deep but which does not qualify as deep according to a given philosophical definition of deep disagreement, or an instance that qualifies as deep according to the philosophical definition but which is not intuitively deep. Ranalli (Reference Ranalli2021) and Ranalli and Lagewaard (Reference Ranalli and Lagewaard2022a) appear to be tacitly committed to this method when they criticize several technical definitions of deep disagreement for their inadequacy in matching our intuitions about real and hypothetical cases of disagreement. Regarding Lynch’s definition of deep disagreement mentioned above, they note, for example, that adopting this definition would mean not categorizing moral disagreements – such as those concerning the wrongness of murder or the moral status of fetuses – as deep, because they are plausibly rooted in moral or metaphysical principles rather than epistemic ones, even though they seem intuitively deep.
A second way of implementing the metaphysical project involves treating the various definitions found in specialized scholarship as revisionary analyses of the lay concept. To the best of my knowledge, this alternative has not been explored in the scholarship so far, but it is worth mentioning in light of the forthcoming discussion. A revisionary analysis does not aim at describing an existing concept – whether a folk concept or a concept from an earlier stage of inquiry – but at replacing it with a new one that is considered more efficient in serving a certain function or purpose. Revisionary analyses are common in all branches of inquiry. An often-discussed example is the definition of “planet” accepted at the 2006 conference of the International Astronomical Union (IAU).Footnote 4 Until the 21st century, there was not a precise definition of what a planet was. The concept was rather ostensively defined through its nine paradigmatic instances. However, in the early 21st century, astronomers discovered certain “trans-Neptunian objects” such as Eris. These objects were similar to Pluto in certain respects and to asteroids in others. Given the deficiency of the traditional concept of planet in unequivocally classifying such bodies, a revision of the traditional concept was required. There were two candidates. According to one proposal, “planet” should be defined as a celestial object that (a) orbits the Sun and (b) is sufficiently large for its own gravity to have formed it into a sphere. The second proposal retains these two conditions but adds a third: (c) the object must have cleared its neighborhood of debris. Following a vote, the International Astronomical Union (IAU) decided in 2006 to adopt the second alternative. This replaced the traditional concept, and astronomers now use it for celestial classification.
As might already be anticipated, the criteria used for adjudicating competing proposals of revisionary analysis differ from those employed for arbitrating between competing proposals of descriptive analysis. While maintaining some resemblance to the original concept is desirable in revisionary analysis, similarity is commonly viewed merely as a tiebreaker criterion.Footnote 5 The primary criterion for adopting a proposal is its superior ability to fulfill the intended function compared to both the old concept and other contenders. The reason for preferring the current concept over the old concept of planet and over the first proposal of revision is its superior ability to provide a simple yet consistent classification of celestial bodies. Now, if theoretical models of deep disagreement are revisions of the folk concept, the question of which one better represents our pre-theoretical intuitions about the nature of deep disagreements takes a backseat. There are two different questions we should ask instead: First, what are the functional deficiencies inherent in the folk concept that justify its replacement? Second, which among the candidates for replacing the old concept better fulfills this function?
Further on in the text, I will elaborate on these points. It’s worth noting at the outset that this paper aims to challenge the possibility of using both methodologies as a model for thinking about technical definitions of deep disagreements. Philosophical concepts of deep disagreement should not be reconstructed as offering either descriptive or revisionary analyses of the folk concept of deep disagreement. Before developing the arguments for this view, I consider in Section 2 a rather expedited way of challenging the metaphysical program. It consists in denying the existence of a folk concept of deep disagreement to be (descriptively or revisionarily) analyzed. Given the strong evidence for a non-philosophical concept, I reject this view. In Section 3, after providing the argument against the metaphysical program, I advance a new model for thinking about technical concepts of deep disagreement that I call “explanatory analysis.” An explanatory analysis does not aim at describing the meaning of a concept nor at replacing it with a new, more fitting one. Instead, it aims at revealing the underlying structure of the phenomena that fall under the extension of the target concept. In the conclusions, I draw two consequences of viewing technical concepts of deep disagreement through the model provided by explanatory analysis. The first is that, contrary to the assumptions made by scholars participating in the metaphysical program, these concepts are not necessarily competitive or mutually exclusive. A second implication of my account is that the concept of deep disagreement is not methodologically dispensable, as some critics of the metaphysical program have recently argued.
2. The common-sense notion of deep disagreement
It is clear that for the concepts of deep disagreement we find in the scholarship being either descriptive or revisionary analyses there needs to be a pre-theoretical, common-sense notion of deep disagreement. As we saw earlier, descriptive analyses aim at understanding the meaning attached to a concept by a certain language community. It is clear that if technical concepts are intended as descriptive analyses, the only candidate for occupying the place of the targeted language community is the community of folk English speakers. It is difficult to imagine another language community for which “deep disagreement” could have an established meaning. For the same reason, we must assume the existence of a lay notion in order to make sense of technical concepts being revisionary. As previously noted, revisionary analyses are essentially suggestions about how to improve the meaning commonly attached to a concept. But what could be the already established concept that is improved by philosophical definitions of deep disagreement, if not the common-sense notion?
Given the indispensability of a common-sense notion of deep disagreement for the viability of the metaphysical program, an expedient way of challenging it consists in denying the existence of a common-sense notion of “deep disagreement.” This line of criticism was recently explored by Guido Melchior in a paper published in this same journal. He contends that “deep disagreement” is a “purely technical term,” because “there is no commonly shared concept of deep disagreement and no corresponding common-sense notion in any natural language” (2024, 10). Although he does not define what a purely technical term is, the subsequent discussion suggests that he believes “deep disagreement” is a term of art, as there are many in philosophy – such as “synthetic a priori” as used by Kant or “performative” as used by Austin – which did not previously exist in ordinary language and whose meanings were stipulatively fixed. From this, Melchior concludes that the use of assessment techniques proper to descriptive analysis or to ameliorative perspectives (his preferred example of revisionary analysis is Carnapian explication) for evaluating definitions of deep disagreement is methodologically flawed:
Deep disagreement is not a common-sense concept like knowledge, belief, or truth. Accordingly, we cannot analyze it in the same way we analyze these other epistemic concepts by comparing them with our pre-theoretical intuitions. In this respect, the metaphysical program of investigating the nature of deep disagreement by providing a conceptual analysis, a descriptive definition, or a Carnapian explanation is methodologically mistaken. (Melchior Reference Melchior2024, 13–14)
Departing from the same premise, Melchior goes as far as to argue that the term “deep disagreement” lacks theoretical relevance and proposes its elimination from specialized literature. Since the term does not refer to a single phenomenon, its continued use as an umbrella term for phenomena that are, in fact, very heterogeneous is potentially confusing and offers no theoretical benefit. Instead, scholars should begin to refer to the different types of disagreement encompassed so far under the label of “deep disagreement,” using different terms such as “hinge-disagreements” or “disagreements on fundamental epistemic principles.” Questions such as whether deep disagreements are rationally irresoluble should be replaced by the question of whether “hinge-disagreements” or “disagreements on fundamental epistemic principles” are rationally irresoluble.
Admittedly, Melchior”s view on the status of technical concepts of deep disagreement is prima facie plausible. “Deep disagreement” does not feature prominently in our everyday language acquisition, and its meaning is not elucidated by any English dictionary. However, a strong prima facie case for the existence of a folk concept of deep disagreement could be made if two facts could be established: a) the term “deep disagreement” has an extended use in non-philosophical language; b) this use is consistent, i.e., there is a recognizable pattern in the different instances to which the term is applied. If there were such a pattern, it would be reasonable to suppose that the set of traits defining the pattern constitutes the meaning of the expression. Fortunately, for the purpose of this paper, both facts can be convincingly proven.
The term “deep disagreement” has been informally used long before the onset of philosophical discussions on deep disagreements, and it continues to be used beyond the confines of philosophical scholarship by individuals who know little or nothing about the philosophical discussion on deep disagreement. This can be attested by searching for the use of the term in newspapers and databases. A search for the term in The Washington Post yielded results of more than 8000 instances of the term’s use in news and opinion articles. A similar search in the academic database JSTOR registered over 1400 uses of the expression, including articles, books, and reviews, the vast majority of which do not belong to the literature on deep disagreements. An additional search on Google Books for the use of the term prior to 1985, i.e., before the publication of Fogelin’s paper, yielded over 6,500 instances of the use of the expression in books and newspapers.
The disagreements described as “deep” within this broad sample of textual sources are varied in several respects. While some arise in informal settings, such as social networks and mass media, others occur in more formal, structured contexts like academic or legal forums. Many concern the appropriateness of different social goals – spanning areas like education, healthcare, employment, economics, environmental management, and public safety – while others focus on the means and policies for achieving these goals. Some disagreements classified as deep relate strictly to factual questions (often within the natural sciences, social sciences, and humanities), while a significant portion also addresses value-laden issues in the realms of law, ethics, and aesthetics. This diversity might initially suggest a lack of common traits connecting the various instances. However, as we look beyond this diversity, a set of underlying similarities emerges, revealing a stable and recognizable pattern of disagreement characterized by the following traits:
-
a) Sociality: The disagreements ranked as deep usually involve large groups of people, often impacting communities or entire societies.
-
b) Relevance: They normally pertain to significant issues with wide-reaching implications.
-
c) Heatedness: They are often marked by intense emotions and strong convictions.
-
d) Persistence: They tend to be resistant to resolution through argumentation.
-
e) Fundamentality: They usually touch on essential questions regarding life, rights, morality, or science.
-
f) Intricateness: They characteristically encompass a wide range of topics beyond the primary issue, making them complex.
-
g) Polarization: In disagreement categorized as deep in non-philosophical contexts middle positions are typically absent, with opposing sides taking entrenched stances.Footnote 6
The idea that the concept of deep disagreement is associated with traits like those listed here is not entirely new, as it has precedents in existing scholarship.Footnote 7 For instance, Ranalli and Lagewaard argue that persistence is a necessary condition for deep disagreement (Reference Ranalli and Lagewaard2022a). They also identify “systematicity” or “ripple effect” (referred to here as intricateness) as a necessary condition, a view shared by other scholars (de Ridder Reference de Ridder, Edenberg and Hannon2021; Lavorerio Reference Lavorerio2021b). Polarization has also been cited as a significant feature of deep disagreements (Petterson Reference Patterson2015; de Ridder Reference de Ridder, Edenberg and Hannon2021; Lavorerio Reference Lavorerio2021b), as well as their affective component (Patterson Reference Patterson2015; Aberdein Reference Aberdein, Tanesini and Lynch2020; Lavorerio Reference Lavorerio2021b). However, I believe the characterization provided here improves upon previous ones in several ways. First, earlier characterizations tend to be fragmentary and incomplete, mentioning only a subset of the traits that define the non-philosophical concept of deep disagreement. Second, prior characterizations often treat these traits as effects or merely circumstantial aspects of deep disagreements. For instance, de Ridder suggests that deep disagreements “contribute to different kinds of polarization” (2021, 234), implying that deep disagreements causally foster a state of affairs that is not conceptually tied to them – much like how, say, a sedentary lifestyle fosters heart disease without heart disease being part of the definition of a sedentary lifestyle. Similarly, Andrew Aberdein argues that “deep disagreements are often heated, but not necessarily so” (2020, 44), suggesting, I believe, that heatedness is merely statistically linked to deep disagreement. My account, by contrast, emphasizes that these traits are internally connected to deep disagreements. Additionally, previous works often overlook the fact that it is the non-philosophical concept of deep disagreement being addressed when traits from this list are used to describe deep disagreements. This oversight can lead to confusion. First, scholars referencing the folk concept may believe (or be perceived to believe) that they are advancing their own theory about the nature of deep disagreement, when in fact they are simply describing its meaning in non-philosophical contexts. Second, as is common in scholarship, when these scholars additionally propose a technical concept of deep disagreement, they may inadvertently give the impression of endorsing inconsistent accounts, despite actually working with concepts belonging to different contexts of use (Lavorerio Reference Lavorerio2021b; de Ridder Reference de Ridder, Edenberg and Hannon2021).
By claiming that the traits included in the previous list are part of the common-sense concept of deep disagreement, I do not mean to suggest that they are individually necessary and collectively sufficient for a disagreement to be classified as deep. Rather, the non-philosophical concept of deep disagreement is best understood as a family-resemblance concept. The nature of this kind of concept can be illustrated through the concept of “game,” which Wittgenstein used to introduce the topic in contemporary philosophy.Footnote 8 In section §66 of Philosophical Investigations, he challenges the reader to state a set of conditions that are “common to all games” – a set of characteristics that are individually necessary and collectively sufficient for an activity to be considered a game. If Wittgenstein is right, this challenge cannot be met. Games are leisure activities, but not all games are played for fun. Games are competitive, but there are also cooperative games, such as singing and dancing games. Games are designed to test the skills of the players, but there are games that depend entirely on luck, such as roulette. Games have rules, “but when a child throws his ball at the wall and catches it again, this feature has disappeared” (Wittgenstein Reference Wittgenstein1953, §66).
Broadly stated, in a family resemblance concept, an item’s classification does not depend on exhibiting a set of necessary and collectively sufficient traits but on possessing certain traits that are typical of that class. The more of these traits an item possesses, the more natural or appropriate its inclusion in the class becomes. Conceiving ordinary deep disagreements under the model of a family resemblance concept involves thinking of characteristics such as persistence or polarization not as necessary for a disagreement to qualify as deep, but rather as typical traits, as features that contribute to make it deep. The more of these characteristics are present in a disagreement, the more natural or appropriate it will be to describe it as deep.Footnote 9
A consequence of the fact that members of a family resemblance class have only typical traits is that borderline cases are to be expected (cf. Ben-Yami Reference Ben-Yami, Glock and Hyman2017; Ma and van Brakel Reference Ma and van Brakel2015). On one side of the spectrum are the cases that possess all the typical traits of the class and whose membership is indisputable (the “paradigmatic” instances). On the opposite side are the cases that clearly do not satisfy enough typical traits to be considered members of the class. However, because it is indeterminate how many typical traits are necessary for class membership, there can be cases in between these two extremes where it is difficult or even impossible to rationally decide whether they belong to the class or not. These are the “borderline” cases. This point might also be relevant for deep disagreements. Alongside the paradigmatic instances of deep disagreement (those that exhibit all the listed traits) and disagreements that clearly lack a sufficient number of these traits, there could be instances of disagreements where it is difficult or impossible to determine whether they exhibit enough of these traits to be classified as deep. These are the borderline cases of deep disagreement.Footnote 10
As also noted in the scholarship on family resemblance concepts, the indeterminacy of family-resemblance concepts can be exacerbated by the fact that the typical traits of a class could themselves designate further family resemblance classes (Hanfling Reference Hanfling1989). Consider a feature such as skill. After arguing that “game” is a family resemblance concept, Wittgenstein comments: “Look at the parts played by skill and luck, and at the difference between skill in chess and skill in tennis.” (Wittgenstein Reference Wittgenstein1953, §66). The point of this remark seems to be that skill, a typical trait of games, is itself related by family resemblances. If this is right, then the challenge of determining whether an activity is a game or not may arise not only from uncertainty about whether a sufficient number of typical features are present in a particular activity, but also from uncertainty about whether each of these features is present in an acceptable measure.
This kind of indeterminacy could also affect deep disagreements because not only is class membership gradual but arguably also because several of their typical traits can be gradually instantiated as well. Opinions in a disagreement can lean more or less toward the extremes, the debate can be more or less heated, and disagreements can resist rational resolution for varying lengths of time. This can lead to uncertainty about whether, in a given debate, opinions are sufficiently divided to be considered “polarized,” or whether the time elapsed since the disagreement’s emergence is long enough to qualify as “persistent.” As a result, we may be uncertain about whether a disagreement qualifies as deep, not only because it lacks several of the typical traits of deep disagreements, but also because the traits that are present may not be optimally expressed.
Anticipating possible objections, Wittgenstein asks in the same context whether a blurred concept can be called a concept at all. The point is relevant to our purposes because the above remarks on the non-philosophical concept of deep disagreement might have created the impression that reconstructing it as a family resemblance concept is perilously close to denying the existence of such a concept altogether. Wittgenstein approaches the question rather rhetorically. He asks whether an unsharp photograph of a person is still a photograph and whether we should say that a person who says to another “Stay roughly here” has not said anything at all. The answers are clear: blurred pictures are still pictures, and imprecise orders are still orders. Both are able to convey information, albeit in a vague manner. Applied to our problem, we can acknowledge that describing a disagreement as deep in non-philosophical terms might be a fuzzy description. However, it remains an informative description nonetheless. It asserts that the disagreement in question exhibits a substantial number of the traits typical of deep disagreements and that each trait present is instantiated to a considerable degree.
It can contribute to the understanding of the nature of the lay concept of deep disagreement to compare it with technical notions found in the scholarship. In contrast to the lay concept, technical concepts generally refer to well-defined classes. For instance, Michael Lynch outlines four individually necessary and collectively sufficient conditions for a disagreement to be classified as deep. Along with Mutual Circularity (the disagreement centers on principles that cannot be justified without circular reasoning), he identifies Commonality (both parties share a common epistemic goal), Competition (the parties endorse distinct principles within a given domain, where (a) these principles prescribe different methods as most reliable, and (b) these methods generate incompatible beliefs), and Non-arbitration (no mutually accepted epistemic principle exists to resolve the disagreement) (Lynch Reference Lynch, Haddock, Millar and Pritchard2010, 265). There is little doubt that these conditions are intended not only to be individually necessary and collectively sufficient but also to express a precise and clear-cut notion in each case. Another definition mentioned at the beginning of this paper states that a deep disagreement occurs when the disagreeing parties are committed to inconsistent hinges. Although the idea of a hinge in Wittgenstein’s philosophy is notoriously fuzzy and vague, Duncan Pritchard has attributed it a precise meaning within the context of his research on deep disagreement. According to him, a “hinge” refers to any commitment that satisfies each of the following conditions: being not optional, tacit, a-rational, and held with optimal certainty (Pritchard Reference Pritchard2018, pp. 2–3). It is clear from the context that these notions are intended to refer to concepts with clear edges as well.Footnote 11
3. The relation between technical and non-philosophical notions of deep disagreement explained
Having established the existence of a folk concept of deep disagreement and described its salient characteristics, we are now in a better position to investigate whether technical concepts are related to it in some way. Two possibilities have already been suggested: that scholars, by advancing technical concepts, aim to describe the lay concept, or that they intend these concepts as revisions of the lay concept. These are the two possibilities open to the metaphysical program, the program that aims to provide criteria for arbitrating between different technical concepts of deep disagreement. In the first part of this section, it will be argued that technical concepts of deep disagreement are not related to the lay concept in any of these ways. In the second part, a better model for apprehending the relationship will be suggested.
Assessing scholarly concepts of deep disagreement by examining how well they accommodate cases of disagreement that intuitively seem deep is, at best, an uncharitable strategy. To understand why, it is important to note that technical concepts of deep disagreement typically presuppose a rich philosophical background. Lynch’s notion of deep disagreement, for example, explicitly draws on David Hume’s treatment of induction—a principle fundamental to many of our epistemic practices yet, as the Scottish philosopher argued, one that cannot be supported by non-circular reasoning. Lynch’s idea of a deep disagreement is, in essence, a scenario in which agents confront each other with principles that hold the same fundamental status as induction does for Hume. Pritchard’s definition provides another example of the theoretical weight that technical concepts of deep disagreement often carry. As noted earlier, he defines deep disagreement as a clash of hinges, a notion rooted in Wittgenstein’s On Certainty. According to this theory, rational evaluation in any epistemic domain presupposes a relatively fixed set of foundational commitments, or “hinges,” which lie beyond doubt and are not open to rational scrutiny.
Given that the lay concept of deep disagreement is used by individuals who are unfamiliar with such philosophical theories, it is implausible to suppose that the meaning they ascribe to “deep disagreement” has any connection to those theories. Moreover, since it is unlikely that scholars are unaware of this implausibility, we can conclude that the concepts they advance (which have highly theoretical associations) aim at a different purpose than describing the meaning of the lay concept. Furthermore, if we accept that any definition should be assessed based on how well it achieves its intended goals, then technical definitions should be evaluated according to distinct objectives.
When we inquire into these objectives, one might be tempted to shift to the opposite side of the descriptive-revisionary analysis dichotomy, asserting that technical concepts aim to improve upon the lay concept. If this were the case, assessing technical concepts – and ultimately selecting one as the correct instantiation—would require first understanding the flaws that scholars have identified in the lay concept of deep disagreement and then determining which of the technical concepts found in the scholarly literature addresses these flaws most effectively. Returning to our paradigmatic instance of revisionary analysis, the revision of the concept of “planet” in astronomy, this is how we should proceed if we wanted to understand the reasons that lead astronomers to forge a new concept. We should first inquire about the theoretical deficiencies identified in the traditional concept of a planet, and then ask why the new concept is better suited to address them. However, in the scholarship on deep disagreement, no mention is made of alleged flaws in the folk concept of disagreement. Unlike well-known examples of revisionary analysis, the development of technical concepts of deep disagreement is never preceded by a diagnosis of deficiencies in the lay concept. The best explanation for this omission is that the proposal of such concepts is not driven by a revisionary aim concerning the folk concept.
Given the difficulties in interpreting technical concepts of deep disagreement either as descriptions or as attempted revisions of the lay concept, one might be tempted to suppose that philosophical reflection has no interest at all in the lay concept of deep disagreement. We would then disagree with Melchior about the existence of a folk concept, but agree with him about its irrelevance to research on deep disagreements. Additionally, it would be merely coincidental that both technical and lay concepts share the same name. Before accepting this view, however, let us consider the prospects of conceiving philosophical concepts through a model not yet discussed – one that we can term “explanatory analysis.”
As with descriptive and revisionary analyses, explanatory analysis usually targets a folk concept. However, unlike descriptive analysis, its goal is not just to capture the meaning of the folk concept, nor, unlike revisionary analysis, to replace it with one deemed superior in some respect. Its aim is to uncover the underlying structures of the entities that fall within the extension of the targeted folk concept. John Locke, the first to draw attention to this type of analysis, provides the concept of gold as an example. While in ordinary language “gold” refers to a yellow, malleable, ductile, and nearly incorrodible metal, chemistry seeks a definition tied to the “internal constitution” of the entities called gold in common speech. (Locke Reference Locke1975).Footnote 12 In modern chemistry, this definition refers to its specific atomic weight. It is evident that chemical “gold” carries a very different meaning than pre-scientific “gold.” However, it is not a coincidence that both concepts share the same name. The scientific concept was designed to illuminate the underlying non-observable properties of the substance denoted by the folk concept and to explain, in conjunction with different scientific laws, the phenomenal properties of “gold” as ordinarily understood.Footnote 13 The folk concept and its corresponding explanatory concept are like two sides of the same coin: each refers to different dimensions of the same phenomenon. They can be used interchangeably (as is the case with the folk and theoretical concepts of gold in chemistry books) depending on the aspect one wishes to emphasize.
If we now turn our attention to the technical concepts of deep disagreement, there are good reasons to view these concepts as attempts to explain the items encompassed by the ordinary concept. Two similarities between technical concepts of deep disagreement and paradigmatic explanatory concepts stand out. First, like the chemical analysis of gold, philosophical analyses of “deep disagreement” are articulated within the language of a theory. Similar to a notion such as “atomic weight” (and unlike notions such as “polarization” or “persistence”), terms like “framework proposition,” “belief system,” “hinge commitment,” or “fundamental epistemic principle” derive their meaning from being situated within a network of concepts provided by a theory of epistemic justification. In the second place, the terms that define technical concepts of deep disagreement, like those defining paradigmatic cases of explanatory concepts, refer to properties that seem to lean more toward the non-observational side of the divide between observable and unobservable properties. We can observe that a certain debate is heated by noting the reactions of its participants or that it is persistent by checking historical records. However, we cannot check in the same way that incompatible framework propositions or incompatible fundamental epistemic principles are at play in a debate. That a proposition holds the status of a framework proposition or a fundamental epistemic principle means that it stands in certain logical relations to other propositions. This status cannot be observationally established but can only be determined in a strictly reflective and speculative manner.
However, for the case regarding the explanatory status of theoretical concepts in relation to the folk concept to be convincing, an additional piece of evidence should be provided. As our discussion about descriptive and revisionary analysis has shown, understanding the intentions behind an analysis—whether it seeks to reflect an existing concept or to ameliorate it—is essential for properly categorizing and assessing it. The same holds true for explanatory analysis: it would be unfair to categorize a concept as explanatory of another if the first was not developed with the intention of addressing the items that fall under the second. So, an argument is needed to show that technical concepts of deep disagreement are developed with the intention of explaining the sources of deep disagreement as commonly conceived.
A prima facie plausible argument against this assumption is the absence of any statement in the scholarship on deep disagreement indicating that concepts of deep disagreement must address deep disagreements as commonly conceived. However, this argument is questionable. By the same token, we would need to refrain from claiming that chemical metal concepts are explanatorily related to pre-theoretical metal concepts. As a matter of fact, there is no statement in chemistry books to the effect that the analysis of each metal concept must explain the structure of the metals (and only those) that fall under the extension of the homonymous folk concept. However, an explicit statement to that effect is unnecessary. The explanatory link between metal concepts and common-sense metal concepts is evident in the practice of chemistry itself. For instance, if an instructor aims to experimentally demonstrate to students that the atomic weight of gold corresponds to its value in chemical theory, they will select a metal sample within the pre-theoretical extension of “gold”—not, for example, one within the common-sense extension of “iron.” In a similar way, even without an explicit statement, it could be convincingly argued that theoretical concepts of deep disagreement are designed to explain deep disagreements as commonly understood, if the types of samples scholars select as instantiations of their theoretical models consistently fall under the common-sense concept. This is precisely what the history of the research field demonstrates.
The history of research on the topic shows that, as a rule, the instances scholars have chosen to instantiate the different theoretical models are cases of disagreement that satisfy the conditions for being deep in a non-philosophical sense. This is evident in the very paper that initiates this research field. In his work, Fogelin not only develops a theoretical concept of deep disagreement grounded in notions such as “structural proposition” and “form of life,” but also illustrates it with two instances paradigmatically deep according to the folk concept: the disagreement on the morality of abortion and the disagreement on the justice of affirmative action measures.Footnote 14 Since Fogelin”s text, all major theoretical perspectives have shared the same concern with explaining the nature of paradigmatic instances of the lay concept. The list includes the disagreement between creationists and evolutionists on the age of the Earth (Lynch Reference Lynch2016), the debate between theists and atheists about God”s existence (Pritchard Reference Pritchard2018), the conflict between liberals and conservatives on the justice of taxation (Aikin Reference Aikin2019), the debate over the benefits of mass vaccination programs (Dare Reference Dare2013), the disagreement between classical logicians and dialetheists on the universality of the principle of non-contradiction (Martin Reference Martin2019), the Brexit controversy (Carter Reference Carter, Hannon and de Ridder2021), and several others.
The chemical analysis of gold has so far served well in this paper to illuminate the general traits of explanatory analysis and shed light on some intriguing aspects of theoretical concepts of deep disagreement, as it stands as a paradigm of explanatory analysis. However, as will be argued shortly, technical concepts of deep disagreement represent non-paradigmatic instances of explanatory analysis, and we should be wary of attributing to them all the properties found in the gold case. One way in which the chemical analysis of gold is exemplary of explanatory analysis is by its capacity to account for all instances falling under the extension of the folk concept of gold. It would indeed be very surprising if a substance were found that satisfied the conditions for being gold as commonly understood but did not satisfy the conditions for being gold in a theoretical sense, or vice versa.Footnote 15 However, in some explanatory analyses, the correspondence between the extension of both the theoretical and folk concepts tends to be less extensive. When medicine progressed in the study of the pathology commonly known as “hearing loss,” for example, it was established that it has different etiologies. For each of these factors, distinct technical concepts were coined, each addressing only a segment of the extension of the folk concept: “sensorineural hearing loss,” “conductive hearing loss,” and “mixed hearing loss.” (Thayer Sataloff and Roehm Reference Thayer Sataloff and Roehm2024). The explanatory concepts are still referred to by the folk term, but a prefix is added to differentiate them.
Similarly to this last example, it doesn’t seem we should expect that a single concept of deep disagreement be able to explain every instance of deep disagreement commonly conceived. The meaning of “deep disagreement,” as the term is commonly used, leads us to expect that its extension is vast. In fact, in real argumentative contexts, there is a large number of disagreements that exhibit the traits typical of deep disagreements according to the folk concept or at least a good portion of them. Expecting a single theory of deep disagreement to account for all of them seems unreasonable. For example, it would be implausible to assume that every such disagreement stems from parties adhering to conflicting fundamental epistemic principles or from the adoption of divergent belief systems. It is more plausible to suggest that disagreements falling within the extension of the folk concept have diverse etiologies. Some may indeed arise from conflicting fundamental epistemic principles, while others might be better explained by differences in the “hinges” of the parties’ belief systems or by the presence of conflicting “underlying normative commitments.” Similar to the case of hearing loss, a prefix could be added to those folk disagreements that are theoretically accountable, indicating the specific structural factor involved—for example, “conceptual deep disagreements,” “hinge deep disagreements,” and so forth.
Arguably, technical concepts of deep disagreement are even less paradigmatic than our hearing loss example of explanatory analysis. While it is not expected in otolaryngology that a single model accounts for all instances of hearing loss, it is nevertheless expected that every relevant instance of hearing loss (in the ordinary sense of the term) be accounted for by some theoretical model. However, this contention is difficult to sustain in the case of deep disagreements. With highly likelihood that some disagreements under the extension of the folk concept cannot be explained by a theory of deep disagreement. The reason for this is that some deep disagreements as commonly conceived might be the product of rather circumstantial factors, such as parties behaving dogmatically, mishandling evidence, or lacking epistemic competence. Since theoretical models of deep disagreement posit structural factors – such as the parties being committed to fundamental epistemic principles or hinge commitments – these disagreements cannot be accounted for by a theory of deep disagreement. Take, for example, the disagreement between flat-earthers and professional astronomers, which exhibits all the traits of being deep according to the folk concept. If it were the case, as many people believe, that such disagreement does not arise from the parties being committed to different hinges, belief systems, or any other structural factor, but rather from one party being seriously biased and lacking epistemic competence, then this disagreement could not be accounted for by any theory of deep disagreement.Footnote 16
4. Conclusions
Two possible ways of implementing the metaphysical program were examined. The first approach interprets theoretical concepts as descriptions of the lay concept of deep disagreement and employs the method of cases to arbitrate between them. The second approach regards theoretical concepts as revisions of the lay concept of deep disagreement, relying on the criteria provided by revisionary analysis for their assessment. Both alternatives were rejected as inadequate. The reason for considering the metaphysical program methodologically flawed, however, is not that there is no common-sense notion of deep disagreement, but rather that the metaphysical program misunderstands the import of such definitions regarding the folk concept. Theoretical models of deep disagreement are hypotheses about the possible sources of deep disagreements non-philosophically conceived.
Now, a consequence of viewing technical concepts of deep disagreement as providing a non-paradigmatic kind of explanatory analysis is that contrary to the assumptions made by scholars participating in the metaphysical program, these concepts are not necessarily competitive or mutually exclusive. The preceding discussion revealed that it is a misunderstanding to think there can be a method for selecting just one theory of deep disagreement as the correct one. Even the fact that a theory could explain more instances of the folk concept of deep disagreement than another theory does not indicate that the first is correct and the second false. It merely shows that the structural factors identified by the first are more prevalent in real debates than those identified by the second. It is much like discovering that “sensorineural hearing loss” is more common than “conductive hearing loss.”
A second implication of my account is that the concept of deep disagreement is not methodologically dispensable, as some critics of the metaphysical program have recently argued. The common-sense notion of deep disagreement delineates the horizon of problems that theories of deep disagreement should ultimately address and strive to explain. By stating this, I do not mean to suggest that the best-known theories of deep disagreement have, in fact, succeeded in convincingly explaining relevant cases of folk deep disagreements. Indeed, the empirical analyses presented by the major theories of deep disagreement often appear as no more than preliminary sketches or proposals for future development. Some recurring shortcomings can be outlined.
Although the disagreements analyzed in the scholarship are often referred to by the names of notorious empirical cases – such as the creationism debate or the heliocentrism debate – doubts sometimes arise as to whether the scholar is truly referring to these debates or to mere “possible” but fictitious (toy) cases that carry the same name as the real ones. In other cases, where there is little doubt that the analysis is intended to reflect a debate occurring in a real setting, doubts arise as to whether the example truly instantiates the structural traits postulated by the model. For instance, a scholar might claim that certain commitments assumed by the parties in a particular debate have the status of “hinges” or that the parties involved operate within different “belief systems,” but little effort is made to address prima facie doubts concerning such claims. Finally, doubts often arise concerning the conclusions that the scholar draws about the resolvability (or irresolvability) of the case in point based on the structural aspects identified in the analysis. When this deficiency occurs, it may be beyond doubt that the example refers to an empirical case, and it could be conceded that the debate is rooted, for example, in opposing “hinges” or “belief systems,” but it remains unclear why this fact necessarily determines whether the disagreement is resolvable (or irresolvable). In principle, nothing prevents these issues from being addressed, and doing so would allow scholarship on deep disagreement to progress toward increasing its empirical relevance.
Open access
