Robert Barnard

In the past, experimental philosophers have explored the psychological underpinning of a number of notions in philosophy, including free will, moral responsibility, and more. But prior to this chapter, although a number of philosophers have speculated on how ordinary folks might, or should, think about the liar paradox, no one had systematically explored the psychological underpinnings of the Liar itself. The authors take on this task. In particular, the chapter investigates the status of a liar sentence, L = ‘Sentence L is false’. The thesis, arrived at by interpreting the data the authors have accrued, is that reflective thinkers (some of whom possess a modicum of philosophical expertise) judge L to be neither true nor false (as opposed to false or true), and the authors see this as some evidence for the claim that L _is_ neither true nor false.

This chapter articulates a version of correspondence theory that holds that truth is always correspondence. Separating questions about the nature of truth from questions about the correct ontology permits a metaphysically neutral position. When assertoric language is deployed in such a way that its singular terms and unnegated existential quantifications carry ontological commitment to particulars that putatively belong to the right ontology and its predicates carry ontological commitment to properties and relations that putatively belong to the right ontology, then correspondence functions in what is called a _direct_ way. The chapter holds that truth is always correspondence, but is rarely direct, and propositions native to different discourses can all be literally true via correspondence, although very often their truth constitutes an indirect kind of correspondence that does not require the right ontology to include objects, properties, or relations answering to the proposition’s singular, predicative, or existential-quantificational constituents.

The time has come to consider whether experimental philosophy’s (“x-phi”) early arguments, debates, and conceptual frameworks, that may have worn well in its early days, fit with the diverse range of projects undertaken by experimental philosophers. Our aim is to propose a novel taxonomy for x-phi that identifies four paths from empirical findings to philosophical consequences, which we call the “fourfold route.” We show how this taxonomy can be fruitfully applied even at what one might have taken to be the furthest edges of possible applications of x-phi in metaphysics and formal philosophy. Ultimately, the fourfold route helps us understand a different kind of empirical fact: the development of x-phi itself.

A typical guiding principle of an account of truth is: “truth is objective,” or, to be clear, judging whether an assertion is true or false depends upon how things are in the world rather than how someone or some community believes it to be. Accordingly, whenever a claim is objectively true, its truth conditions ought not depend upon the context in which it is uttered or the utterer making the claim. Part of our ongoing empirical studies surveying people’s responses to questions about truth involved prompts on objectivity. Our studies suggest the following: overall, individuals tend to endorse claims that are consistent with the objectivity of truth; not all conceptions of objectivity are equal, even people who endorse the objectivity of truth sometimes assent to one form of truth’s objectivity over other forms; philosophers and non-philosophers both endorse the objectivity of truth, but the apparent commitment of philosophers is stronger.

Philosophical theorizing about truth manifests a desire to conform to the ordinary or folk notion of truth. This practice often involves attempts to accommodate some form of correspondence. We discuss this accommodation project in light of two empirical projects intended to describe the content of the ordinary conception of truth. One, due to Arne Naess, claims that the ordinary conception of truth is not correspondence. Our more recent study is consistent with Naess’ result. Our findings suggest that contextual factors and respondent gender affect whether the folk accept that correspondence is sufficient for truth. These findings seem to show that the project of accommodating the ordinary notion of truth is more difficult than philosophers had anticipated because it is fragmentary.

Ontological Naturalism holds that our fundamental ontology contains only those generally natural objects, properties, and relations required by our best scientific theory. Logical principles are thought of as being normative of correct inference and as involving necessary truths and relations. Necessary relations are stronger than the relations described by science; norms are traditionally thought to be separate from the descriptive project of science. Yet, ontological theories, including ontological naturalism, employ logic freely without offering an account of logical normativity and necessity. It appears that logical properties and relations are prima facie non-natural. If so, then ontological naturalism paradoxically presupposes the presence of non-natural properties and relations as a part of the ultimate fundamental ontology. I explore this tension between logic and ontology as a means to clarifying the standards of acceptability for ontological theories generally and as a means to clarifying the character of logical discourse. I conclude that all proposed ontological theories must provide a substantive account of logic which respects its intrinsic modal and normative character as a minimal test of meta-ontological acceptability.

Many of Tarski’s better known papers are either about or include lengthy discussions of how to properly define various concepts: truth, logical consequence, semantic concepts, or definability. In general, these papers identify two primary conditions for successful definitions: formal correctness and material adequacy. Material adequacy requires that the concept expressed by the formal definition capture the intuitive content of truth. Our primary interest in this paper is to better understand Tarski’s thinking about material adequacy, and whether components of his view developed over time. More precisely, we are concerned with how Tarski’s understanding of the content of the common-sense, every-day usage of truth may have developed over time. We distinguish this concern from the character of the extensional criterion of adequacy Tarski proposes: that a materially adequate definition must entail all instances of Convention T. We will develop our reading of Tarski as follows: first, we will review the “Polemical Remarks,” focusing primarily on §§14 and 17, and Tarski’s references to Naess’ empirical research. Next, we will provide a summary and discussion of Naess’ work, especially his findings with respect to Tarski’s definition of truth and his research that suggests there is no single common or everyday concept of truth. Third, we will consider several possible objections to our interpretation of the Tarski–Naess dialectic. We will conclude that Tarski’s conception of material adequacy developed over time, potentially because of what he had learned through his interactions with Naess.

The liar paradox is widely conceived as a problem for logic and semantics. On the basis of empirical studies presented here, we suggest that there is an underappreciated psychological dimension to the liar paradox and related problems, conceived as a problem for human thinkers. Specific findings suggest that how one interprets the liar sentence and similar paradoxes can vary in relation to one’s capacity for logical and reflective thought, acceptance of certain logical principles, and degree of philosophical training, but also as a function of factors such as religious belief, gender, and whether the problem is treated as theoretical or practical. Though preliminary, these findings suggest that one reason the liar paradox resists a final resolution is that it engages both aspects described by so-called dual process accounts of human cognition.

This Philosophical Companion collects sixteen papers organized by theme and sequence to follow the broad outline of a generic course in the logic of first-order quantification. The papers range from 5-34 pages in length and vary widely in degree of technical difficulty. Most of the papers have previously appeared, and only one – the editor’s contribution—was written specifically for the volume. With the publication of this excellent little book, Hughes therefore provides a useful template for the instructor who wants to instill a deeper appreciation of the philosophical side of the discipline in his or her students and fills the gap created when older anthologies such as Copi and Gould’s Readings on Logic or Strawson’s Philosophical Logic went out of print. While similar to each of these classic volumes, the present text is unique in its focus on first order logic; Copi and Gould emphasized topics better suited to an introductory level course while the Strawson text covers topics which are on the one hand slightly more advanced and on the other marked by their historical context.