1. The idea of triangulation, understood as the interaction between two individuals and aspects of their shared environment, figures prominently in Donald Davidson's reflections during the second part of his philosophical career. And yet, most of the reactions to his work either neglect this idea or misrepresent its role in his thinking. Robert H. Myers and Claudine Verheggen have written a book that rectifies this; they spell out, and extensively build on, Davidson's triangulation argument.Footnote ¹ They show not only that the argument is perfectly continuous with Davidson's earlier papers on radical interpretation, but also that it vindicates assumptions he had made in those papers; it is thus indispensable for a proper understanding of Davidson's thoroughly systematic view. Furthermore, Myers and Verheggen reveal the relevance of the triangulation argument for a broad range of questions in contemporary philosophy. This special issue, which began in 2018 as an authors-meet-critics symposium at the Canadian Philosophical Association Annual Congress in Montreal, is devoted to their development of the triangulation argument. It consists in the responses of three critics, Kirk Ludwig, Alexander Miller, and Paul Hurley, followed by Verheggen's and Myers's replies. Miller addresses the first part of the book, authored by Verheggen, while Hurley addresses the second part, authored by Myers. Ludwig discusses both. I shall offer a brief sketch of each of the two parts of the book. Each sketch will be followed by an overview of the questions raised by the critics.

2. In Part One, Verheggen explains the argument and defends it against the main objections that have been raised against it. The central question that Verheggen is concerned with is: what makes language and thought possible? More specifically, what makes it possible for conditions of correctness, which are essential to language and thought, to be determined? I shall call this ‘the constitutive question.’ As Verheggen sees it, the triangulation argument establishes that the idea of triangulation — that is, the idea of repeated interaction with another individual and features of the shared world — is a necessary ingredient in any acceptable answer to that question. Only an individual who has triangulated can have language and thoughts. I do not have the space for a full reconstruction of her interpretation of the argument here. I shall limit myself to indicating why this interpretation is unique, and why the version of semantic non-reductionism that Verheggen articulates on its basis is novel.

Usually, Davidson's remarks on triangulation are taken to amount to at least two distinct arguments, one for the claim that triangulation is required for the determination of the meanings of one's expressions and the contents of one's thoughts, the other for the claim that triangulation is required for the possession of the concept of objectivity. Verheggen argues that, for Davidson, the determination of meaning and content — more specifically, of the conditions of correctness that govern them — requires the recognition, by the individual, of the distinction between correctness or incorrectness, and thus the possession of the concept of objectivity. Possessing this concept requires, in turn, that the individual interact linguistically with another individual and, simultaneously, with their shared world. It is only through such triangular interactions that features of the world can actively be singled out by individuals and thereby become objects of thought and speech. Thus, Verheggen shows that there is only one triangulation argument, which purports to establish a necessary link between the determination of correctness conditions governing the utterances and thoughts of an agent and the possession of the concept of objectivity by that agent.

It might be thought that the answer to the constitutive question is circular, for it suggests that what determines correctness conditions must in some sense already involve such conditions. But the argument, as reconstructed by Verheggen, also reveals why circularity cannot altogether be avoided, and why any reductionist conception of meaning is hopeless. Furthermore, what sets her account apart from other views is that the non-reductionist aspect of the account is the result of taking the constitutive question seriously and confronting it head-on, rather than diagnosing it as misguided and dismissing it. Her account is thus different from non-reductionist views, such as the ones defended by John McDowell and Barry Stroud, according to which we do not seem to be able to say more about the determination of meaning than that words mean what they do because we mean what we do by them. Indeed, Verheggen develops a constructive, as opposed to quietist, non-reductionist view, which yields a necessary connection between having a language and thoughts, on the one hand, and engaging in triangular interactions with another individual and features of the shared world, on the other. The account offers resources for illuminating interventions in several contemporary debates.

One such debate concerns the normativity of meaning. Verheggen's answer to the constitutive question reveals meaning to be doubly normative, though in neither case is the normativity categorical. First, it shows that if one means something by one's words, then one must have distinguished, on some occasions at least, between correct and incorrect applications of those words, and thus one must have normative attitudes toward one's and others’ uses of expressions. These attitudes, however, are semantic attitudes, rather than pre-semantic attitudes of primitive normativity of the sort that Hannah Ginsborg has advanced. Second, it shows that speakers themselves contribute to the constitution of the conditions of correct application that make their expressions meaningful. This in turn suggests that speakers cannot be indifferent to them, or to the hypothetical prescriptions that can be derived from them, without jeopardizing them. This, Verheggen thinks, sets meaning apart from other natural phenomena (to which we can be indifferent without thereby posing a threat to their existence) in a way that entitles us to characterize it as normative.

Another debate concerns externalism, which is the view according to which what we mean and think depends, in part, on things that are external to us. As Verheggen interprets it, Davidson's brand of externalism differs from other externalist views, including those defended by Hilary Putnam, Tyler Burge, and interpreters of Ludwig Wittgenstein such as Saul Kripke and Meredith Williams. It blends physical with social externalism by taking interactions with both the external world and another individual to be necessary for the determination of meaning. Moreover, the physical aspect of the externalist view is grounded in its social aspect, for external features of the world cannot play the role of determinants of meaning unless they are singled out in triangular exchanges. This shows, contra Putnam, that the external features that determine meaning need not be those pertaining to the microstructure of the world. It also shows, contra Burge, that what an individual means by her expressions need not align with what those expressions mean in the community of speakers to which she belongs. Davidson's social externalism is thus interpersonal, rather than communitarian.

Verheggen also articulates the anti-sceptical upshot of the argument. The Cartesian sceptic takes it for granted that it is possible for one to have the beliefs that one has and for the world to be altogether different from what one's beliefs suggest it is. But the theory of content that the triangulation argument affords reveals this assumption to be false. If the contents of our basic beliefs about the world are necessarily determined by their external causes, then our beliefs cannot be both contentful and largely false. Our picture of the world must be by and large right, or so Verheggen argues against Stroud, who contends that Davidson is entitled only to the conclusion that the practice of belief attribution is truth-ascribing. Our picture of the world is also justified, or so Verheggen argues against McDowell's criticism of Davidson. For even though, as McDowell insists, it is the product of causal influence from the world, such influence can make our utterances and thoughts contentful only if it is conceptualized by triangulating agents. The causes that provide the content of our beliefs also justify those beliefs.

The triangulation argument shows why internal features, be they mental or physical, cannot contribute to the determination of meaning, given that they are not the sort of features that can be triangulated upon. It thus vindicates not only the externalist starting point of the argument, but also long-standing Davidsonian assumptions, such as the claim that meaning is essentially public, and the claim that one cannot have beliefs unless one is aware of the possibility of being mistaken. Furthermore, the triangulation argument provides additional support to the holistic aspect of the Davidsonian view, according to which the contents of our utterances and attitudes cannot be determined in isolation from other utterances and attitudes. Triangulators cannot render some meanings and contents determinate without at the same time rendering many others so.

3. In his contribution, Ludwig discusses Verheggen's reconstruction and defence of the triangulation argument. He grants that her reconstruction captures Davidson's view, but claims that the argument does not succeed. He begins by noting that it relies on the anti-Cartesian assumption that thought contents are determined by something independently specifiable, an assumption that Ludwig alleges to be unsupported. He then examines the prospects for motivating this determination assumption by invoking the publicity of thought content. But he concludes that the justification for the publicity of thought content in fact relies on that assumption, and thus cannot justify it. It might be thought that the assumption is vindicated by the triangulation argument itself, insofar as the argument shows how thought contents are determined. However, Ludwig argues that, if we follow Verheggen and accept that the facts about an individual considered in isolation cannot determine content, we will have no choice but to accept that introducing a second individual to the picture will not make a difference. Ludwig does not challenge the claim that having a language and thoughts requires having the concept of objectivity. Rather, he argues that having this concept does not require triangulating with another individual.

Unlike Ludwig, Miller does not take issue with the triangulation argument in his contribution. Instead, he raises a series of questions about its consequences. First, he casts doubt on the second way in which Verheggen takes meaning to be normative. Recall that this is the idea that, given that speakers must contribute to the determination of the conditions of correct application of their expressions, they cannot be indifferent to these conditions or to the hypothetical prescriptions that can be derived from them. Against this, Miller argues that being involved in the constitution of a fact is compatible with subsequently becoming indifferent to it, and that even if we accept that speakers cannot be indifferent to the conditions of correctness that are essential to meaning on pain of compromising them, this does not show that meaning is essentially normative. Second, he argues that Verheggen is wrong to treat Kripke's sceptical solution to the paradox about meaning as a form of communitarianism, and that a proper interpretation of that solution is consistent with Davidsonian interpersonal externalism. Miller then challenges Verheggen to indicate similarities and differences between Crispin Wright's non-reductionist view and Davidson's view. He wonders about what a Davidsonian response to Wright's challenge to reconcile the first-person epistemology of intentional attitudes with their dispositional nature might look like, as well as about the relationship between what one means by an expression and one's judgements about what one means by that expression in triangular contexts.

4. In Part Two of the book, Myers develops in detail the implications of the triangulation argument for the practical domain. The constitutive question here becomes: what makes normative thought (and talk) so much as possible? The triangulation argument suggests that the content of agents’ normative attitudes is in the first instance fixed through their triangular interaction with others and with the normative features of the world they share. Myers undertakes to show that we should accept this extension of the argument to the practical realm. He argues that, on the one hand, normative beliefs do have contents of the sort that calls for the kind of explanation that the triangulation argument offers, and, on the other hand, the world does have normative features of the sort that can be triangulated upon. Moreover, he argues that the Davidsonian view he articulates has the resources to account for the special normative authority claimed by morality.

Davidson's commitment to the causal theory of action seems to demand that we view the desires of a given agent as mere dispositions to act in whatever ways appear to her to lead to their fulfilment. This picture is typically taken to entail a conception of normative beliefs as depending upon desires in such a way that they cannot have content in the manner required by the triangulation argument. Myers argues that Davidson need not conceive of normative beliefs in this way, for his commitment to the causal theory is in fact compatible with his viewing normative beliefs as prior to desires. In order to recognize this compatibility, we must tease apart two Humean ideas that tend to be conflated, namely the Humean theory of motivation, according to which only desires can move us to act, and the Humean theory of desire, according to which desires are nothing more than functional states. On Myers's interpretation, Davidson rightly accepts the former, while rightly rejecting the latter. Davidson does not deny that desires are required for motivation, but he conceives of them as responsive to the normative reasons agents take themselves to have for acting in certain ways, and thus as responsive to normative beliefs. To give shape to this Davidsonian view of desires, Myers appeals to the holism of the mental, which, on his reading, characterizes not only the ways in which desires are related to beliefs but also the relations that hold among desires. So understood, the holism of the mental indicates that desires partake in the systemic aim of arriving at the truth, which is constitutive of the mental. More specifically, desires, as a system, aim to get normative matters right, which accounts for their sensitivity to normative beliefs. And, given that the aim of getting normative matters right is systemic, rather than constitutive of each desire, plenty of room is left for unruly desires and other deviations from the aim. Agents are imperfect, but what makes them agents is the pursuit of truth in both the descriptive and the normative domains.

After articulating the Davidsonian account of desires as shaped by normative beliefs, Myers turns to the question of the nature of those beliefs, and shows that it is plausible to think of them as determined, in part, by the world, in the manner suggested by the triangulation argument. The challenge at this stage is to make a convincing case for the claim that there are normative features in the world on which we may triangulate, a claim that strikes many as deeply implausible. Myers proceeds to address the most important worries that have been articulated about normative realism. He shows that Davidson has the resources to respond to Christine Korsgaard's complaint to the effect that features that are entirely external from us cannot exert normative authority, to J.L. Mackie's complaint to the effect that normative features can only be metaphysically queer, and to Gilbert Harman's complaint to the effect that such features are explanatorily redundant, and thus not required in our theorizing. Myers argues that we should attribute to Davidson a conception of normative properties as primary, rather than secondary, qualities. Also, he thinks that anomalous monism is able to answer satisfactorily not only the question of how mental elements can be involved in causal transactions, but also the broader question of how normative elements can be so involved.

Myers then considers the topic of moral reasons. He argues that, unlike other realist views, the Davidsonian view can account for the existence of agent-relative as well as agent-neutral reasons. While basic normative reasons are agent-neutral in character, normative reasons may also depend, in part, on the relations that agents come to bear to particular situations, which indicates that agents might have special reasons for action in virtue of those relations. However, this reinforces the intuitively plausible idea that agents might have reasons to act that put them in conflict with one another. Myers argues that the Davidsonian view is equipped to sustain the contractualist thought, familiar from the work of T.M. Scanlon, that all agents share second-order reasons to transcend that conflict by interacting with each other on terms of mutual respect. Importantly, though, these second-order reasons can be conceived of as agent-neutral, which makes it possible to account for the authority of morality more successfully than Scanlon himself does. Finally, Myers reconsiders the question of whether Kantian constructivism, of the sort espoused by Korsgaard, offers an even more compelling account of morality's authority. He shows that the considerations to which constructivists appeal in defending that account take for granted a conception of content that constructivism lacks the resources to articulate. The fact that the Davidsonian version of realism springs, in part, from a theory of content, and, more generally, from a systematic account of the relation between minds and the world, makes it not only unique among the metaethical options, but also philosophically powerful.

5. In his contribution, Ludwig challenges Myers's thinking about the Humean theory of desire. Myers claims that there are cases in which we are not disposed to perform a certain kind of action (such as unnerving our opponents during a game of chess) not because of some countervailing desire but because performing an action of that kind would not be a way of conforming to the reasons we take ourselves to have for our initial desire (such as wanting to win at chess for the sake of developing a valuable skill). This shows, he thinks, that the Humean theory of desire cannot be right. Ludwig retorts that adequate explanations of such cases can be given entirely by way of desires, and without appealing to reasons, provided that we understand the Humean conception of desire to be more sophisticated than Myers assumes. Ludwig then argues that Davidson himself subscribes to a sophisticated Humean theory of this sort. Finally, Ludwig suggests that discerning someone's normative beliefs does not require that we take those beliefs to be responses to normative features of the world. As he sees it, we can detect normative beliefs in others by identifying the functional roles such beliefs play in guiding behaviour. What is more, he thinks that the existence of sociopaths shows that we can understand each other without sharing normative concepts.

Hurley also challenges Myers's interpretation of Davidson's view of desire. Unlike Ludwig, however, he agrees that Davidson rejects the Humean theory. The disagreement between Hurley and Myers concerns the specific, anti-Humean, way in which Davidson conceives of the aim of desires to get normative matters right. As we have seen, a central feature of Myers's view is that this aim is systemic; it belongs to desires considered as a whole. This makes it possible for individual desires to diverge from it. Hurley, however, thinks that this is a distortion of Davidson's view. As Hurley sees it, Davidson follows in the footprints of G.E.M. Anscombe in thinking that desires aim at the good individually, rather than systemically, and thus that an agent cannot intelligibly want something unless she takes the object of her desire to be good. Thus, though Hurley and Myers agree that Davidson sees an essential link between our conative psychology and our engagement with the normative domain, Hurley views this link as fastening to individual desires, rather than to the whole of desires in the way suggested by Myers. Importantly, Hurley thinks that, in order for an agent to be in a position to take things to be desirable or good, and thereby engage in an attempt to alter the world, she must attend not only to that world, but also to the ways in which other agents might alter it, and thus to their desires. Hurley takes this process to be tantamount to triangulation, and concludes that his alternative interpretation is perfectly compatible with the triangulation argument. Thus, on his reading, the argument requires a conception of normative judgements as justified through practical reasoning, and as capable of exhibiting objectivity in this way. What it does not require, indeed, what Davidson, as Hurley reads him, warns against, is thinking that the world has, independently of us, normative features that we aim to get right.