Constitutivism argues that the source of the categorical force of the norms of rationality and morality lies in the constitutive features of agency. A systematic failure to be guided by these norms would amount to a loss or lack of agency. Since we cannot but be agents, we cannot but be unconditionally guided by these norms. The constitutivist strategy has been challenged by David Enoch. He argues that our participation in agency is optional and thus cannot be a source of (...) categorical demands. In this paper, I defend the viability of constitutivism by showing that agency is indeed a special ‘inescapable’ enterprise. Agency has the largest jurisdiction, and it is closed under rational assessment. This inescapability does not exempt constitutivism from raising the question whether agents have reason to be agents, but this question has to be taken up within agency. If this question is answered affirmatively, then—I argue—the criteria of practical correctness are self-ratifying in a non-circular way. This is sufficient to show the viability of the constitutivist strategy. Whether agents have conclusive reasons to be agents, however, is a matter to be addressed in the terms of particular versions of constitutivism. (shrink)

It is often argued that future-directed decisions are effective at shaping our future conduct because they give rise, at the time of action, to a decisive reason to act as originally decided. In this paper, I argue that standard accounts of decision-based reasons are unsatisfactory. For they focus either on tie-breaking scenarios or cases of self-directed distal manipulation. I argue that future-directed decisions are better understood as tools for the non-manipulative, intrapersonal division of deliberative labor over time. A future-directed decision (...) to ϕ gives rise to a defeasible exclusionary reason to ϕ. This reason is grounded on the default authority that is normally granted to one’s prior self as an “expert” deliberator. I argue that this kind of exclusionary reason is the only one that can account for the effectiveness of future-directed decisions at shaping our diachronic agency without violating our autonomy over time. (shrink)

In this paper, I argue against the popular philosophical thesis---aka the ‘own action condition’---that an agent can only intend one’s own actions. I argue that the own action condition does not hold for any executive attitude, intentions included. The proper object of intentions is propositional rather than agential (‘I intend that so-and-so be the case’ rather than ‘I intend to do such-and-such’). I show that, although there are some essential de se components in intending, they do not restrict the content (...) of intentions to one’s own actions. I then discuss the special way in which one’s own actions can figure in the content of one’s intentions, which shows that the distinction between intending and acting is less stark than it appears at first. This is a conclusion that many defenders of the own action condition might find appealing but which, I argue, is better supported by rejecting the own action condition. (shrink)

In this paper I investigate whether there are genuine and irreducible pressures of diachronic rationality grounded on the structure of the subject rather than on substantive considerations, such as pragmatic ones. I argue that structural pressures of diachronic rationality have a limited scope. The most important pressure only tells against arbitrary interference with the mechanisms for the retention of attitudes over time. I then argue that in the practical case, a substantial account in terms of the agent's temporal identity appears (...) more promising than a purely structural one, but in the end it still leaves many questions about diachronic practical rationality underdetermined. (shrink)

I review recent work on Phenomenal Conservatism, the position introduced by Michael Huemer according to which if it seems that P to a subject S, in the absence of defeaters S has thereby some degree of justification for believing P.

This chapter discusses the structure of our temporally extended agency. We do not have the power to act directly at a distance, so any of our temporally extended projects must be sustained over its temporal unfolding by momentary actions. We need both the capacity to organize these momentary steps in light of a synoptic overview of the extended activity as a whole and to sustain our motivation to continue to pursue the extended activity. Hence, the distinctive mode in which we (...) act over time is that of ’planning agency,’ which requires a form of temporal identification that goes beyond mere psychological continuity. I then discuss the differences in internal structure between merely continuous and integrated activities, and between telic and atelic ones. I provide a taxonomy of the different kinds of temporal goods and values and how these structures might bear on the risk of crisis of meaning in our temporal existence. I then touch briefly on the issue of how our mortality might make a difference to the structure of what we find valuable and how it relates to the temporal features of our agency. In the closing section, I discuss the effects of the moving temporal location of the agent (with her local executive powers) relative to her extended pursuits, including the asymmetries generated by the distinction between past and future stages of the activity and the moving horizon of what the agent can anticipate and (indirectly) control. (shrink)

One type of argument to sceptical paradox proceeds by making a case that a certain kind of metaphysically “heavyweight or “cornerstone” proposition is beyond all possible evidence and hence may not be known or justifiably believed. Crispin Wright has argued that we can concede that our acceptance of these propositions is evidentially risky and still remain rationally entitled to those of our ordinary knowledge claims that are seemingly threatened by that concession. A problem for Wright’s proposal is the so-called Leaching (...) worry: if we are merely rationally entitled to accept the cornerstones without evidence, how can we achieve evidence-based knowledge of the multitude of quotidian propositions that we think we know, which require the cornerstones to be true? This paper presents a rigorous, novel explication of this worry within a Bayesian framework, and offers the Entitlement theorist two distinct responses. (shrink)

Crispin Wright maintains that the architecture of perceptual justification is such that we can acquire justification for our perceptual beliefs only if we have antecedent justification for ruling out any sceptical alternative. Wright contends that this principle doesn’t elicit scepticism, for we are non-evidentially entitled to accept the negation of any sceptical alternative. Sebastiano Moruzzi has challenged Wright’s contention by arguing that since our non-evidential entitlements don’t remove the epistemic risk of our perceptual beliefs, they don’t actually enable us to (...) acquire justification for these beliefs. In this paper I show that Wright’s responses to Moruzzi are ineffective and that Moruzzi’s argument is validated by probabilistic reasoning. I also suggest that Wright cannot answer Moruzzi’s challenge without weakening the support available for his conception of the architecture of perceptual justification. (shrink)

Crispin Wright has given an explanation of how a first time warrant can fall short of transmitting across a known entailment. Formal epistemologists have struggled to turn Wright’s informal explanation into cogent Bayesian reasoning. In this paper, I analyse two Bayesian models of Wright’s account respectively proposed by Samir Okasha and Jake Chandler. I argue that both formalizations are unsatisfactory for different reasons, and I lay down a third Bayesian model that appears to me to capture the valid kernel of (...) Wright’s explanation. After this, I consider a recent development in Wright’s account of transmission failure. Wright suggests that his condition sufficient for transmission failure of first time warrant also suffices for transmission failure of supplementary warrant. I propose an interpretation of Wright’s suggestion that shield it from objections. I then lay down a fourth Bayesian framework that provides a simplified model of the unified explanation of transmission failure envisaged by Wright. (shrink)

In this paper, I will discuss the various ways in which intentions can be said to be conditional, with particular attention to the internal conditions on the intentions’ content. I will first consider what it takes to carry out a conditional intention. I will then discuss how the distinctive norms of intention apply to conditional intentions and whether conditional intentions are a weaker sort of commitments than the unconditional ones. This discussion will lead to the idea of what I call (...) the ‘deep structure’ of intentions. Roughly, this is the idea that the conditional nature of our intentions is only partially made explicit in the expressions we use to communicate our intentions and in the explicit form of our thinking about and reasoning with them. Most conditions that qualify our intentions are part of a deep functional structure that can be evinced by observing the actual psychological functioning of intentions and by considering the rational requirements that they engage. I will argue that the deep structure of intentions is characteristically conditional. Genuinely unconditional intentions are only limiting instances of conditional intentions and their contribution to agency can only be understood in light of this fact. I will conclude by showing that the characteristic conditional structure of intentions is intimately related to distinctive features of human agency, especially to its unity over time. (shrink)

What can the philosophy of agency learn from Nguyen’s book on games? The most important lesson concerns, to use Nguyen’s terms, the ‘layered’ structure of our agency and the ‘fluidity’ requ...

The subject of Labelled Non-Classical Logics is the development and investigation of a framework for the modular and uniform presentation and implementation of non-classical logics, in particular modal and relevance logics. Logics are presented as labelled deduction systems, which are proved to be sound and complete with respect to the corresponding Kripke-style semantics. We investigate the proof theory of our systems, and show them to possess structural properties such as normalization and the subformula property, which we exploit not only to (...) establish advantages and limitations of our approach with respect to related ones, but also to give, by means of a substructural analysis, a new proof-theoretic method for investigating decidability and complexity of (some of) the logics we consider. All of our deduction systems have been implemented in the generic theorem prover Isabelle, thus providing a simple and natural environment for interactive proof development. Labelled Non-Classical Logics is essential reading for researchers and practitioners interested in the theory and applications of non-classical logics. (shrink)

Timothy Smiley’s wonderful paper ‘Rejection’ (1996) is still perhaps not as well known or well understood as it should be. This note first gives a quick presentation of themes from that paper, though done in our own way, and then considers a putative line of objection – recently advanced by Julien Murzi and Ole Hjortland (2009) – to one of Smiley’s key claims. Along the way, we consider the prospects for an intuitionistic approach to some of the issues discussed in (...) Smiley’s paper. (shrink)

Recent works in epistemology show that the claim that coherence is truth conducive – in the sense that, given suitable ceteris paribus conditions, more coherent sets of statements are always more probable – is dubious and possibly false. From this, it does not follows that coherence is a useless notion in epistemology and philosophy of science. Dietrich and Moretti (Philosophy of science 72(3): 403–424, 2005) have proposed a formal of account of how coherence is confirmation conducive—that is, of how the (...) coherence of a set of statements facilitates the confirmation of such statements. This account is grounded in two confirmation transmission properties that are satisfied by some of the measures of coherence recently proposed in the literature. These properties explicate everyday and scientific uses of coherence. In his paper, I review the main findings of Dietrich and Moretti (2005) and define two evidence-gathering properties that are satisfied by the same measures of coherence and constitute further ways in which coherence is confirmation conducive. At least one of these properties vindicates important applications of the notion of coherence in everyday life and in science. (shrink)

According to Jim Pryor’s dogmatism, when you have an experience with content p, you often have prima facie justification for believing p that doesn’t rest on your independent justification for believing any proposition. Although dogmatism has an intuitive appeal and seems to have an antisceptical bite, it has been targeted by various objections. This paper principally aims to answer the objections by Roger White according to which dogmatism is inconsistent with the Bayesian account of how evidence affects our rational credences. (...) If this were true, the rational acceptability of dogmatism would be seriously questionable. I respond that these objections don’t get off the ground because they assume that our experiences and our introspective beliefs that we have experiences have the same evidential force, whereas the dogmatist is uncommitted to this assumption. I also consider the question whether dogmatism has an antisceptical bite. I suggest that the answer turns on whether or not the Bayesian can determine the priors of hypotheses and conjectures on the grounds of their extra-empirical virtues. If the Bayesian can do so, the thesis that dogmatism has an antisceptical bite is probably false. (shrink)

As systems based on opaque Artificial Intelligence (AI) continue to flourish in diverse real-world applications, understanding these black box models has become paramount. In response, Explainable AI (XAI) has emerged as a field of research with practical and ethical benefits across various domains. This paper not only highlights the advancements in XAI and its application in real-world scenarios but also addresses the ongoing challenges within XAI, emphasizing the need for broader perspectives and collaborative efforts. We bring together experts from diverse (...) fields to identify open problems, striving to synchronize research agendas and accelerate XAI in practical applications. By fostering collaborative discussion and interdisciplinary cooperation, we aim to propel XAI forward, contributing to its continued success. Our goal is to put forward a comprehensive proposal for advancing XAI. To achieve this goal, we present a manifesto of 27 open problems categorized into nine categories. These challenges encapsulate the complexities and nuances of XAI and offer a road map for future research. For each problem, we provide promising research directions in the hope of harnessing the collective intelligence of interested stakeholders. (shrink)

John Hardwig has championed the thesis (NE) that evidence that an expert EXP has evidence for a proposition P, constituted by EXP’s testimony that P, is not evidence for P itself, where evidence for P is generally characterized as anything that counts towards establishing the truth of P. In this paper, I first show that (NE) yields tensions within Hardwig’s overall view of epistemic reliance on experts and makes it imply unpalatable consequences. Then, I use Shogenji-Roche’s theorem of transitivity of (...) incremental confirmation to show that (NE) is false if a natural Bayesian formalization of the above notion of evidence is implemented. I concede that Hardwig could resist my Bayesian objection if he re-interpreted (NE) as a more precise thesis that only applies to community-focused evidence. I argue, however, that this precisification, while diminishing the philosophical relevance of (NE), wouldn’t settle the tensions internal to Hardwig’s views. (shrink)

How psychopaths and their capacity for moral action are viewed is not only philosophically interesting but is also important and relevant for policy. The philosophical discussion of psychopathy has focussed upon the psychological faculties that are prerequisites for moral responsibility and empirical findings regarding psychopathy that are relevant to philosophical accounts of moral understanding and motivation. However, there are legitimate worries about whether psychopathy is a robust scientific construct, and there are risks attached to reifying psychopathy or other psychiatric constructs. (...) We defend the concept of psychopathy by pointing out the relevance of empirical studies about it for our ordinary practices of ascribing moral responsibility and folk psychological accounts of moral understanding and motivation. (shrink)

First collected in Italy in 1985, _Art's Claim to Truth_ is considered by many philosophers to be one of Gianni Vattimo's most important works. Newly revised for English readers, the book begins with a challenge to Plato, Aristotle, Kant, and Hegel, who viewed art as a metaphysical aspect of reality rather than a futuristic anticipation of it. Following Martin Heidegger's interpretation of the history of philosophy, Vattimo outlines the existential ontological conditions of aesthetics, paying particular attention to the works of (...) Kandinsky, which reaffirm the ontological implications of art. Vattimo then builds on Hans-Georg Gadamer's theory of aesthetics and provides an alternative to a rationalistic-positivistic criticism of art. This is the heart of Vattimo's argument, and with it he demonstrates how hermeneutical philosophy reaffirms art's ontological status and makes clear the importance of hermeneutics for aesthetic studies. In the book's final section, Vattimo articulates the consequences of reclaiming the ontological status of aesthetics without its metaphysical implications, holding Aristotle's concept of beauty responsible for the dissolution of metaphysics itself. In its direct engagement with the works of Gadamer, Heidegger, and Luigi Pareyson, _Art's Claim to Truth_ offers a better understanding of the work of Vattimo and a deeper knowledge of ontology, hermeneutics, and the philosophical examination of truth. (shrink)

In this paper, I discuss whether there are genuinely *diachronic* constraints of practical rationality, that is, pressures on combinations of practical attitudes over time, which are not reducible to mere synchronic rational pressures. Michael Bratman has recently argued that there is at least one such diachronic rational constraint that governs the stability of intentions over time. *Pace* Bratman, I argue that there are no genuinely diachronic constraints on intentions that meet the stringent desiderata set by him. But I show that (...) there are at least two synchronic rational constraints with distinctive and important, although only indirect, diachronic dimensions. Neither of them, however, supports the practical conservatism in the face of normative underdetermination that, according to Bratman, is part and parcel of the diachronic rationality of intention stability. (shrink)

In this paper, I discuss Ludwig's systematic and illuminating account of conditional intentions, with particular reference to my own view (presented in "Conditional Intentions", Noûs, 2009). In contrast to Ludwig, I argue that we should prefer a formal characterization of conditional intentions rather than a more substantial one in terms of reasons for action (although the conditions that qualify an intention bear on the reasonableness and justifiability of the intention). I then defend a partially different taxonomy of the conditions that (...) might qualify an intention and discuss how the difference bears on the application of the rational pressures of intention. I go on to acknowledge that Ludwig is correct on insisting on the centrality of the *epistemic* element in the antecedent of conditional intentions. But I argue that even when a condition has been settled (that is, when the agent has ascertained that it holds), the intention remains genuinely conditional. In my view, conditions that have been settled are not just part of the background of planning: they continue to qualify the content of the intention (although they come to play a different role when settled). I then discuss how the settling of a condition does not interrupt the *continuity* of the content and structure of the intention---in contrast to Ludwig's account, where the conditional intention appears to give rise, when the conditions are taken as settled, to a distinct *unconditional* intention. I close by discussing the serious concern that my way of characterizing conditional intentions threatens to swallow most intentions, given that it is unlikely that we have intentions that do not rest on our accepting the obtaining of relevant conditions. (shrink)

According to the perceptual view of language comprehension, listeners typically recover high-level linguistic properties such as utterance meaning without inferential work. The perceptual view is subject to the Objection from Context: since utterance meaning is massively context-sensitive, and context-sensitivity requires cognitive inference, the perceptual view is false. In recent work, Berit Brogaard provides a challenging reply to this objection. She argues that in language comprehension context-sensitivity is typically exercised not through inferences, but rather through top-down perceptual modulations or perceptual learning. (...) This paper provides a complete formulation of the Objection from Context and evaluates Brogaards reply to it. Drawing on conceptual considerations and empirical examples, we argue that the exercise of context-sensitivity in language comprehension does, in fact, typically involve inference. (shrink)

The purpose of this paper is to explore the connection between change and the B-theory of time, sometimes also called the Scientific view of time, according to which reality is a four-dimensional spacetime manifold, where past, present and future things equally exist, and the present time and non-present times are metaphysically the same. I argue in favour of a novel response to the much-vexed question of whether there is change on the B-theory or not. In fact, B-theorists are often said (...) to hold a ‘static’ view of time. But this far from being innocent label: if the B-theory of time presents a model of temporal reality that is static, then there is no change on the B-theory. From this, one can reasonably think as follows: of course, there is change, so the B-theory must be false. What I plan to do in this paper is to argue that in some sense there is change on the B-theory, but in some other sense, there is no change on the B-theory. To do so, I present three instances of change: Existential Change, namely the view that things change with respect to their existence over time; Qualitative Change, the view that things change with respect to how they are over time; Propositional Change, namely the view that things (i.e. propositions) change with respect to truth value over time. I argue that while there is a reading of these three instances of change that is true on the B-theory, and so there is change on the B-theory in this sense, there is a B-theoretical reading of each of them that is not true on the B-theory, and therefore there is no change on the B-theory in this other sense. (shrink)

What are words and how should we individuate them? There are two main answers on the philosophical market. For some, words are bundles of structural-functional features defining a unique performance profile. For others, words are non-eternal continuants individuated by their causal-historical ancestry. These conceptions offer competing views of the nature of words, and it seems natural to assume that at most one of them can capture the essence of wordhood. This paper makes a case for pluralism about wordhood: the view (...) that there is a plurality of acceptable conceptions of the nature of words, none of which is uniquely entitled to inform us as to what wordhood consists in. (shrink)

In this paper we focus on transmission and failure of transmission of warrant. We identify three individually necessary and jointly sufficient conditions for transmission of warrant, and we show that their satisfaction grounds a number of interesting epistemic phenomena that have not been sufficiently appreciated in the literature. We then scrutinise Wright’s analysis of transmission failure and improve on extant readings of it. Nonetheless, we present a Bayesian counterexample that shows that Wright’s analysis is partially incoherent with our analysis of (...) warrant transmission and prima facie defective. We conclude exploring three alternative lines of reply: developing a more satisfactory account of transmission failure, which we outline; dismissing the Bayesian counterexample by rejecting some of its assumptions; reinterpreting Wright’s analysis to make it immune to the counterexample. (shrink)

Some Presentists—according to whom everything is present—identify instants of time with propositions of a certain kind. However, the view that times are propositions seems to be at odds with Presentism: if there are times then there are past times, and therefore things that are past; but how could there be things that are past if everything is present? In this paper, we describe the Presentist view that times are propositions ; we set out the argument that Presentism is incompatible with (...) the view that times are propositions ; and then we describe three possible responses to that argument on behalf of Presentists who identify times with propositions. We argue that each of these responses comes with significant costs. Finally, we describe a fourth possible response—according to which times are irreducibly higher-order entities—which appears to avoid the costs of the other three. We also describe and respond to two objections to the higher-order strategy. (shrink)

We show that if Ƒ is any "well-behaved" subset of the Borei functions and we assume the Axiom of Determinacy then the hierarchy of degrees on $P(^\omega \omega )$ induced by Ƒ turns out to look like the Wadge hierarchy (which is the special case where Ƒ is the set of continuous functions).

The Schön misconduct case has been widely publicized in the media and has sparked intense discussions within and outside the scientific community about general issues of science ethics. This paper analyses the Report of the official Committee charged with the investigation in order to show that what at first seems to be a quite uncontroversial case, turns out to be an accumulation of many interesting and non-trivial questions (of both ethical and philosophical interest). In particular, the paper intends to show (...) that daily scientific practices are structurally permeated by chronic problems; this has serious consequences for how practicing scientists assess their work in general, and scientific misconduct in particular. A philosophical approach is proposed that sees scientific method and scientific ethics as inextricably interwoven. Furthermore, the paper intends to show that the definition of co-authorship that the members of the Committee use, although perhaps clear in theory, proves highly problematic in practice and raises more questions that it answers. A final plea is made for a more self-reflecting attitude of scientists as far as the moral and methodological profile of science is concerned as a key element for improving not only their scientific achievements, but also their assessment of problematic cases. (shrink)

This paper introduces the Monstrous Conclusion, according to which, for any population, there is a better population consisting of just one individual (the Monster). The Monstrous Conclusion is deeply counterintuitive. I defend a version of Prioritarianism as a particularly promising population axiology that does not imply the Monstrous Conclusion. According to this version of Prioritarianism, which I call Asymptotic Prioritarianism, there is diminishing marginal moral importance of individual welfare that can get close to, but never quite reach, some upper limit. (...) I argue that Asymptotic Prioritarianism faces a theoretical cost, that I call the Absolute Priority Principle. However, the Absolute Priority Principle is an extreme version of what I call the Trade-off Condition, an already noteworthy problem facing other (more widely endorsed) versions of Prioritarianism. I conclude that it is better for a theory to imply the Absolute Priority Principle and avoid the Monstrous Conclusion than to imply the Monstrous Conclusion and the Trade-off Condition. The potential for Asymptotic Prioritarianism is substantial. (shrink)

In [9] we have considered a wide class of "well-behaved" reducibilities for sets of reals. In this paper we continue with the study of Borel reducibilities by proving a dichotomy theorem for the degree-structures induced by good Borel reducibilities. This extends and improves the results of [9] allowing to deal with a larger class of notions of reduction (including, among others, the Baire class ξ functions).

This paper analyzes the case of Made in Carcere, an innovative social enterprise providing jobs to one of the most marginalized groups in society: convicted women. Relying on an extensive database that covers 8 years of activity, we propose a micro-level analysis of the processes adopted by Made in Carcere to foster the integral human development of convicted women, its target stakeholders. We show that this complex effort has successfully unfolded through two macro-processes: creating a safe space for experimentation and (...) allowing convicted women to bridge their experience to the outside reality. Our work provides evidence of an organization that successfully confronts the restrictive and dehumanizing setting of prisons by means of market mechanisms that can foster convicted women’s integral human development. (shrink)

Moral constitutivism purports to explain moral normativity by appeal to the nature of either agency or rational powers. Ambitious constitutivism aspires to ground the categorical authority of morality and to derive the content of the basic moral norms while avoiding the problems of moral realism. As a general strategy, moral constitutivism faces three serious challenges. First, the shmagency challenge. The worry is that the authority of the norms derived from the nature of agency is only conditional on having a reason (...) to be an agent rather than some other kind of subject, a shmagent or an alienated agent. Constitutivists usually reply by appealing to the inescapability of agency. Second, there is a worry that agency is too thin a basis for the derivation of the substantive content of moral norms. Finally, there is the worry that constitutivism might be unable to make room for bad actions. The entry considers possible responses by moral constitutivism to these concerns and whether, if these responses are unsatisfactory, moral constitutivism might still have some explanatory power but of a less ambitious sort. (shrink)

The discussion of whether psychopaths are morally responsible for their behaviour has long taken place in philosophy. In recent years this has moved into scientific and psychiatric investigation. Responsibility and Psychopathy discusses this subject from both the philosophical and scientific disciplines, as well as a legal perspective.

Most countries have been struggling with the spread of the COVID-19 pandemic imposing social isolation on their citizens. However, this measure carried risks for people's mental health. This study evaluated the psychological repercussions of objective isolation in 1,006 Italians during the first, especially strict, lockdown in spring 2020. Although varying for the regional spread-rate of the contagion, results showed that the longer the isolation and the less adequate the physical space where people were isolated, the worse the mental health. Offline (...) social contacts buffered the association between social isolation and mental health. However, when offline contacts were limited, online contacts seemed crucial in protecting mental health. The findings inform about the potential downsides of the massive social isolation imposed by COVID-19 spread, highlighting possible risk factors and resources to account for implementing such isolation measures. Specifically, besides some known factors such as physical space availability, the local contagion rate is critical in moderating the link between social isolation and mental health issues, supporting national policies implementing regional tiers of restriction severity. (shrink)

This paper develops a new theory of the morality of promissory obligations. T. M. Scanlon notoriously argued that promising consists in assuring the promisee that we will do something. I disagree. I argue that it is true that promising consists in assuring the promisee, but what the promisor gives to the promisee is not an assurance that they will do something, but that the normative situation is in a certain way.

We present a natural deduction system for dual-intuitionistic logic. Its distinctive feature is that it is a single-premise multiple-conclusions system. Its relationships with the natural deduction systems for intuitionistic and classical logic are discussed.

The non-well-founded set theories described by Aczel (1988) have received attention from category theorists and computer scientists, but have been largely ignored by philosophers. At the root of this neglect might lie the impression that these theories do not embody a conception of set, but are rather of mere technical interest. This paper attempts to dispel this impression. I present a conception of set which may be taken as lying behind a non-well-founded set theory. I argue that the axiom AFA (...) is justified on the conception, which provides, contra Rieger (Mind 109:241–253, 2000), a rationale for restricting attention to the system based on this axiom. By making use of formal and informal considerations, I then make a case that most of the other axioms of this system are also justified on the conception. I conclude by commenting on the significance of the conception for the debate about the justification of the Axiom of Foundation. (shrink)