Proof-theoretic reflection principles are schemas which attempt to express the soundness of arithmetical theories within their own language, e.g., ${\mathtt{{Prov}_{\mathsf {PA}} \rightarrow \varphi }}$ can be understood to assert that any statement provable in Peano arithmetic is true. It has been repeatedly suggested that justification for such principles follows directly from acceptance of an arithmetical theory $\mathsf {T}$ or indirectly in virtue of their derivability in certain truth-theoretic extensions thereof. This paper challenges this consensus by exploring relationships between reflection principles (...) and principles of mathematical and transfinite induction as well as the status of the latter with respect to various foundational characterizations of number theory. (shrink)

This paper explores the relationship borne by the traditional paradoxes of set theory and semantics to formal incompleteness phenomena. A central tool is the application of the Arithmetized Completeness Theorem to systems of second-order arithmetic and set theory in which various “paradoxical notions” for first-order languages can be formalized. I will first discuss the setting in which this result was originally presented by Hilbert & Bernays (1939) and also how it was later adapted by Kreisel (1950) and Wang (1955) in (...) order to obtain formal undecidability results. A generalization of this method will then be presented whereby Russell’s paradox, a variant of Mirimanoff’s paradox, the Liar, and the Grelling–Nelson paradox may be uniformly transformed into incompleteness theorems. Some additional observations are then framed relating these results to the unification of the set theoretic and semantic paradoxes, the intensionality of arithmetization (in the sense of Feferman, 1960), and axiomatic theories of truth. (shrink)

Recent critics have called attention to the alienation of contemporary academics from broad currents of intellectual activity in public culture. The general complaint is that intellectuals are finding a professional home in institutions of higher learning, insulated from the concerns and interests of a wider reading audience. The demands of professional expertise do not encourage academics to work as public intellectuals or to take up social, literary, or political matters in imaginative and perspicuous ways. More problematic is the relative absence (...) of religion in the writings of those who aspire to work as public intellectuals. This essay reviews recent attempts by William Dean, Cornel West, Jean Bethke Elshtain, Stephen Carter, and Robin Lovin to remedy the problem of academic alienation and to address the place of religion in American life. (shrink)

The Knowability Paradox purports to show that the controversial but not patently absurd hypothesis that all truths are knowable entails the implausible conclusion that all truths are known. The notoriety of this argument owes to the negative light it appears to cast on the view that there can be no verification-transcendent truths. We argue that it is overly simplistic to formalize the views of contemporary verificationists like Dummett, Prawitz or Martin-Löf using the sort of propositional modal operators which are employed (...) in the original derivation of the Paradox. Instead we propose that the central tenet of verificationism is most accurately formulated as follows: if φ is true, then there exists a proof of φ Building on the work of Artemov (Bull Symb Log 7(1): 1-36, 2001), a system of explicit modal logic with proof quantifiers is introduced to reason about such statements. When the original reasoning of the Paradox is developed in this setting, we reach not a contradiction, but rather the conclusion that there must exist non-constructed proofs. This outcome is evaluated relative to the controversy between Dummett and Prawitz about proof existence and bivalence. (shrink)

Computationalism holds that our grasp of notions like ‘computable function’ can be used to account for our putative ability to refer to the standard model of arithmetic. Tennenbaum's Theorem has been repeatedly invoked in service of this claim. I will argue that not only do the relevant class of arguments fail, but that the result itself is most naturally understood as having the opposite of a reference-fixing effect — i.e., rather than securing the determinacy of number-theoretic reference, Tennenbaum's Theorem points (...) towards a sense in which portions of our computational vocabulary should be regarded as model-relative. (shrink)

This paper presents a systematic study of the prehistory of the traditional subsystems of second-order arithmetic that feature prominently in the reverse mathematics program of Friedman and Simpson. We look in particular at: (i) the long arc from Poincar\'e to Feferman as concerns arithmetic definability and provability, (ii) the interplay between finitism and the formalization of analysis in the lecture notes and publications of Hilbert and Bernays, (iii) the uncertainty as to the constructive status of principles equivalent to Weak K\"onig's (...) Lemma, and (iv) the large-scale intellectual backdrop to arithmetical transfinite recursion in descriptive set theory and its effectivization by Borel, Lusin, Addison, and others. (shrink)

The goal of this paper is to explore the significance of Montague’s paradox—that is, any arithmetical theory $T\supseteq Q$ over a language containing a predicate $P$ satisfying $P\rightarrow \varphi $ and $T\vdash \varphi \,\therefore\,T\vdash P$ is inconsistent—as a limitative result pertaining to the notions of formal, informal, and constructive provability, in their respective historical contexts. To this end, the paradox is reconstructed in a quantified extension $\mathcal {QLP}$ of Artemov’s logic of proofs. $\mathcal {QLP}$ contains both explicit modalities $t:\varphi $ (...) and also proof quantifiers $x:\varphi $. In this system, the basis for the rule NEC is decomposed into a number of distinct principles governing how various modes of reasoning about proofs and provability can be internalized within the system itself. A conceptually motivated resolution to the paradox is proposed in the form of an argument for rejecting the unrestricted rule NEC on the basis of its subsumption of an intuitively invalid principle pertaining to the interaction of proof quantifiers and the proof-theorem relation expressed by explicit modalities. (shrink)

This paper engages the question ‘Does the consistency of a set of axioms entail the existence of a model in which they are satisfied?’ within the frame of the Frege-Hilbert controversy. The question is related historically to the formulation, proof and reception of Gödel’s Completeness Theorem. Tools from mathematical logic are then used to argue that there are precise senses in which Frege was correct to maintain that demonstrating consistency is as difficult as it can be, but also in which (...) Hilbert was correct to maintain that demonstrating existence given consistency is as easy as it can be. (shrink)

It is commonly held that the natural numbers sequence 0, 1, 2,... possesses a unique structure. Yet by a well known model theoretic argument, there exist non-standard models of the formal theory which is generally taken to axiomatize all of our practices and intentions pertaining to use of the term “natural number.” Despite the structural similarity of this argument to the influential set theoretic indeterminacy argument based on the downward L ̈owenheim-Skolem theorem, most theorists agree that the number theoretic version (...) does not have skeptical consequences about the reference of “natural number” analogous to the ‘relativity’ Skolem claimed pertains to notions such as “uncountable” and “cardinal.” In this paper I argue that recent proposals by Shapiro, Lavine, McGee and Field which aim to distinguish the number and set theoretic indeterminacy arguments by locating extra-mathematical constraints on the interpretation of our number theoretic vocabulary are inadequate. I then suggest that if we consider the manner in which the natural numbers figure in our computational practices – e.g. in characterizing how we compute sums and products or determine prime factorizations – it follows that our application of computational terms such as “computable function” and “tractable computational problem” indirectly uniquely determines their structure. (shrink)

The Paradox of the Knower was originally presented by Kaplan and Montague [26] as a puzzle about the everyday notion of knowledge in the face of self-reference. The paradox shows that any theory extending Robinson arithmetic with a predicate K satisfying the factivity axiom K → A as well as a few other epistemically plausible principles is inconsistent. After surveying the background of the paradox, we will focus on a recent debate about the role of epistemic closure principles in the (...) Knower. We will suggest this debate sheds new light on the concept of knowledge which is at issue in the paradox – i.e. is it a “thin” notion divorced from concepts such as evidence or justification, or is it a “thick” notion more closely resembling mathematical provability? We will argue that a number of features of the paradox suggest that the latter option is more plausible. Along the way, we will provide a reconstruction of the paradox using a quantified extension of Artemovʼs [2] Logic of Proofs, as well as a series of results linking the original formulation of the paradox to reflection principles for formal arithmetic. On this basis, we will argue that while the Knower can be understood to motivate a distinction between levels of knowledge, it does not provide a rationale for recognizing a uniform hierarchy of knowledge predicates in the manner suggested by Anderson. (shrink)

Computational complexity theory is a subfield of computer science originating in computability theory and the study of algorithms for solving practical mathematical problems. Amongst its aims is classifying problems by their degree of difficulty — i.e., how hard they are to solve computationally. This paper highlights the significance of complexity theory relative to questions traditionally asked by philosophers of mathematics while also attempting to isolate some new ones — e.g., about the notion of feasibility in mathematics, the $\mathbf{P} \neq \mathbf{NP}$ (...) problem and why it has proven hard to resolve, and the role of non-classical modes of computation and proof. (shrink)

This dissertation addresses a variety of foundational issues pertaining to the notion of algorithm employed in mathematics and computer science. In these settings, an algorithm is taken to be an effective mathematical procedure for solving a previously stated mathematical problem. Procedures of this sort comprise the notional subject matter of the subfield of computer science known as algorithmic analysis. In this context, algorithms are referred to via proper names of which computational properties are directly predicated )). Moreover, many formal results (...) are traditionally stated by explicitly quantifying over algorithms. These observations motivate the view that algorithms are themselves abstract mathematical objects -- a view I refer to as algorithmic realism. The status of this view is clearly related to that of Church's Thesis -- i.e. the claim that a function is computable by an algorithm just in case it is partial recursive. But whereas Church's Thesis is widely accepted on the basis of several well-known mathematical analyses of algorithmic computability, there is presently no consensus on how we can uniformly identify individual algorithms with mathematical objects. In the first chapter of this work, I attempt to illustrate the theoretical significance of algorithmic realism. I suggest that this view is not only of foundational significance to computer science, but also worth highlighting due to the role algorithms play in the fixation of mathematical knowledge and their relationship to intensional entities such as propositions and properties. Chapter Two presents a formal framework for reducing computational discourse to mathematical discourse modeled on contemporary discussion of mathematical nominalism. Chapter Three is centered on a case study intended to illustrate the technical exigencies involved with defending algorithmic realism. Chapter Four explores various ways in which algorithms might be identified with models of computation. And finally, Chapter Five argues that no such identification can uniformly satisfy all statements of algorithmic identity and non-identity affirmed by computational practice. I suggest that the technical crux of algorithmic realism lies in the necessity of reducing recursive specifications of algorithms to iterative models of computation in a manner which preserves algorithmic identity. (shrink)

Michael Zbaraschuk’s recent article, “Not Radical Enough: William Dean’s Problems with God and History,”1 deserves a published response, because it applies not only to my work but to that of many other philosophical theologians, some of whom read this journal. Before discussing the larger issues, I must attend to an item of scholarly housekeeping. Although Zbaraschuk draws narrowly, i.e., from only two of my books—History Making History (1988) and The Religious Critic in American Culture (1994)—he applies his arguments indiscriminately to (...) my work as a totality, omitting most crucially the score of articles and the book written between 1994 and the present. Of course, there is nothing wrong with an .. (shrink)

Moral injury occurs when a person perpetrates, bears witness to, or fails to prevent an act that transgresses their deeply held moral beliefs. The deeply held moral belief that physicians share is the oath they take when completing their lengthy training and embarking on their career: Put the needs of patients first. In today's American healthcare system, doctors, nurses, and other healthcare providers are increasingly forced to consider the demands of other stakeholders -- insurers, hospitals, even their own financial security (...) -- before the needs of their patients. Whenever they are forced to make a decision that contravenes their patient's best interest, they feel a sting of moral injustice. Over time, these repetitive insults amass into moral injury. Moral injury and its causes help explain why healthcare workers started leaving the field in droves long before the COVID-19 pandemic exposed weaknesses in the US system, why a rich country has such poor outcomes in certain categories, why there is a shortage of young doctors training for critical areas, and why patients feel so frustrated. In If I Betray These Words, Wendy Dean explores and exposes the impacts of moral injury through vividly told stories that are at once bewildering and eye-opening. Her book serves as a roadmap through a healthcare landscape that can be confounding, and at times even hellish, for those who must navigate it, and it suggest alternative routes for healers and their patients. (shrink)

The men and women who serve in the armed forces, in the words of Major General Joseph Caravalho, “sign a blank check, co-signed by their families, payable to the Army, Navy, Air Force, or Marines, up to and including their lives.” It is human nature to consider such a pact in polarized terms; the pact concludes in either a celebratory homecoming or funereal mourning. But in reality, surviving catastrophic injury may incur the greatest debt. The small but real possibility of (...) losing the ability to bear biological children due to genitourinary combat injury has been a topic of discussion in hushed tones, behind closed doors. But as policy changes move the conversation into the open, we must be fully aware of the far-reaching and long-term impacts of decisions on those who have sustained genitourinary injury. In January 2016, Secretary of Defense Ashton Carter outlined a set of reforms that would improve the quality of life for military families by recognizing the importance of maintaining fertility, even in the face of severe injury. This first promising step could build a solid foundation of insuring fertility preservation for wounded service members with genitourinary injury, and it could set a precedent beyond the military for insuring treatment for people who have lost their reproductive capacity. Thus, the ethical challenges raised by the new policy require careful analysis. (shrink)

This chapter contains sections titled: Religious Thought as American Three Elements of American Religious Thought A Brief History The Waning of American Philosophy of Religion.

There is currently great controversy over the contribution antimicrobial use in animal agriculture has made to antimicrobial resistance in pathogenic bacteria with negative consequences for human health. In light of this, the approval process for antimicrobials used in US animal agriculture, known as New Animal Drug Application or NADA, is currently being revised by the federal government. We explore the public deliberations over the development of these new policies focusing our attention on the interaction between pharmaceutical companies and the U.S. (...) Food and Drug Administration. What appears to be an antagonistic public discourse is examined in terms of its ability to simultaneously legitimate the roles of the Food and Drug Administration as the official arbiter of policy on antimicrobial use in animal agriculture and as a protector of the public welfare, as well as the role of pharmaceutical companies as the producers of safe and effective products necessary for the protection of public well-being. (shrink)