O pagine editoriali.indd 1 10/04/19 09:10 pagine editoriali.indd 2 10/04/19 09:10 comitato scientifico / scientific committee Michael Arndt (Eberhard Karls Universität Tübingen), Luca Bellotti (Università di Pisa), Luca Gili (Université du Québec à Montréal), Mauro Mariani (Università di Pisa), Carlo Marletti (Università di Pisa), Pierluigi Minari (Università di Firenze), Enrico Moriconi (Università di Pisa), Giacomo Turbanti (Università di Pisa), Gabriele Usberti (Università di Siena) a–n–a–l–i–t–i–c–a 15 Analitica propone una serie di testi – classici, monografie, strumenti antologici e manuali – dedicati ai più importanti temi della ricerca filosofica, con particolare riferimento alla logica, all'epistemologia e alla filosofia del linguaggio. Destinati allo studio, alla documentazione e all'aggiornamento critico, i volumi di Analitica intendono toccare sia i temi istituzionali dei vari campi di indagine, sia le questioni emergenti collocate nei punti di intersezione fra le varie aree di ricerca. Analitica includes reprints of epoch-making monographs, original researches, edited collections and textbooks on major philosophical themes, with a special focus on logic, epistemology and the philosophy of language. The volumes of the series are designed for undergraduate students and for researchers, to whom they offer updated scholarship. They deal with both the fundamental topics of the various research areas and with the emerging questions to be found at their junctions. pagine editoriali.indd 3 10/04/19 09:10 pagine editoriali.indd 4 10/04/19 09:10 Third Pisa Colloquium in Logic, Language and Epistemology Essays in Honour of Mauro Mariani and Carlo Marletti Edited by Luca Bellotti, Luca Gili, Enrico Moriconi, Giacomo Turbanti Edizioni ETS pagine editoriali.indd 5 10/04/19 09:10 www.edizioniets.com © Copyright 2019 Edizioni ETS Palazzo Roncioni Lungarno Mediceo, 16, I-56127 Pisa info@edizioniets.com www.edizioniets.com Distribuzione Messaggerie Libri SPA Sede legale: via G. Verdi 8 20090 Assago (MI) Promozione PDE PROMOZIONE SRL via Zago 2/2 40128 Bologna ISBN 978-884675519-3 pagine editoriali.indd 6 10/04/19 09:10 Third Pisa Colloquium in Logic, Language and Epistemology Essays in Honour of Mauro Mariani and Carlo Marletti pagine editoriali.indd 7 10/04/19 09:10 pagine editoriali.indd 8 10/04/19 09:10 i i "Libro" - 2019/4/10 - 8:25 - page 9 - #1 i i i i i i CONTENTS Preface 13 Enrico Moriconi The philosophical work of Mauro Mariani 15 Luca Gili The philosophical work of Carlo Marletti 21 Giacomo Turbanti An informal exposition of von Neumann's consistency proof 25 Luca Bellotti Paradoxes and set existence 47 Andrea Cantini On false antecedent in dialetheic entailment 59 Massimiliano Carrara Future contingents, Supervaluationism, and relative truth 69 Roberto Ciuni and Carlo Proietti An informational approach to feasible deduction 89 Marcello D'Agostino From logistiké to logistique: the long travel of a word 117 Miriam Franchella and Anna Linda Callow On the size of infinite sets: some Wittgensteinian themes 139 Pasquale Frascolla i i "Libro" - 2019/4/10 - 8:25 - page 10 - #2 i i i i i i 10 CONTENTS Sellars and Carnap on emergence. Some preliminary remarks 153 Carlo Gabbani Is Aristotle's matter ordinary stuff? 167 Gabriele Galluzzo Knowledge and Ockhamist branching time 181 Pierdaniele Giaretta and Giuseppe Spolaore A dialectical analysis of Metaphysics Θ 3 199 Luca Gili In defense of theories and structures in semantics. Reflections on vector models of meaning 215 Alessandro Lenci Structure versus whole versus one 239 Anna Marmodoro Pragmatism and the limits of science 251 Michele Marsonet A note on the logic of distributed knowledge 263 Pierluigi Minari and Stefania Centrone On Popper's decomposition of logical notions 275 Enrico Moriconi Properties and parts in Williams's trope theory 303 Valentina Morotti Kripke's puzzle. A puzzle about belief? 317 Ernesto Napoli i i "Libro" - 2019/4/10 - 8:25 - page 11 - #3 i i i i i i CONTENTS 11 Ruth Millikan on Gottlob Frege: dismantling an apparent clash 329 Carlo Penco The simplicity of the simple approach to personal identity 347 Andrea Sauchelli Category mistakes and the problem of their semantic status 359 Francesco Spada At the roots of rational expressivism 373 Giacomo Turbanti A notion of internalistic logical validity 389 Gabriele Usberti i i "Libro" - 2019/4/10 - 8:25 - page 12 - #4 i i i i i i i i "Libro" - 2019/4/10 - 8:25 - page 13 - #5 i i i i i i PREFACE ENRICO MORICONI In the fall of 1969, I moved to Pisa to start my undergraduate studies and there I met Mauro Mariani and Carlo Marletti. They were in their second year of university and we were all enrolled in the Scuola Normale Superiore. The atmosphere of the Scuola is special in that students live in residences and spend most of their time together, thereby learning from each other and forming lasting friendships. Carlo and Mauro made an immediate impression on me. Already then Carlo was insightful and brilliant and Mauro was a bibliophile, I daresay he was a bookworm. Despite their capabilities and broad knowledge, they were down to earth and eager to help those who approached them with a philosophical question. Mauro and Carlo were studying logic, epistemology and philosophy of language and they were finding their research paths in these fields. At the beginning of my second university year, when I was looking for a study topic in the same broad domain of all things logical, I naturally spent more time with them, benefitting from their insights and suggestions. Thanks to their inputs, I was prompted to widen my research interests and they provided me with answers to the many doubts I had while I was studying logic, philosophy of mathematics and, more generally, philosophy. At that time, they were focusing on W. V. O. Quine's philosophy. Later, Carlo developed an interest in nominalism and Mauro in modal logics. They eventually broadened their research topics to include Aristotle's logic, philosophy of language, linguistics, and Kripke's semantics for modal logics. Years passing, thanks to the special atmosphere of the Scuola Normale, our friendship became ever deeper and together with Lello Frascolla, Ernesto Napoli, and the late Paolo Casalegno we formed a close group that shared a common research agenda. In the 1980s, Carlo, Mauro and I landed jobs at the Department of Philosophy of the University of Pisa, where our mentors Francesco Barone and Vittorio Sainati were the already established scholars working on logic, philosophy of science, and Aristotle. More recently, we were joined by the much younger Luca Bellotti, who is co-editing this volume. Carlo and Mauro were excellent teachers and their classes included innovative approaches that went beyond the traditional syllabus. Yes, the students had to overcome some difficulties of communication, and not only those raised by the complexities of the philosophical topics treated: Mauro's teaching style was ciri i "Libro" - 2019/4/10 - 8:25 - page 14 - #6 i i i i i i 14 ENRICO MORICONI cuitous and Carlo's was concise, at times elliptical. But they were effective and many of their former students have since secured academic positions all over the world. Two of their former students, Luca Gili and Giacomo Turbanti, together with Luca Bellotti and me, are editing this volume in honor of Carlo and Mauro. It is our pleasure to present this collection of essays in this year 2019 as Carlo and Mauro are turning 70. We thank friends and former students who contributed papers on the favourite research topics of the two honorandi. This volume contains essays originally written for this celebration, and eleven of them are by former students of Carlo and Mauro. I thank all the people who enthusiastically contributed to the project. I thank Valentina Morotti for her precious help in drafting Carlo's and Mauro's bibliographies and Laura Tesconi for editing and type-setting the volume. This Festschrift is a token of friendship and gratitude from us all. Cari Carlo e Mauro, buon compleanno! i i "Libro" - 2019/4/10 - 8:25 - page 347 - #339 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY ANDREA SAUCHELLI andreasauchelli@ln.edu.hk Department of Philosophy, Lingnan University Abstract: I provide a simple solution to the problem of determining the characterising feature(s) of the simple approach to personal identity, sometimes also called the simple view: instead of focusing on claims regarding the analysability, reducibility, or triviality of the concepts used in simple theories of personal identity, I propose instead a metaphysical criterion to define this approach. In particular, I claim that the simple approach is (best seen as) that family of theories according to which personal identity is a relation that essentially depends on a mereologically simple (or impartite) entity the existence and features of which may be known directly (e.g., by introspection) or indirectly (e.g., by deduction from a series of other premises). Keywords: Personal identity, identity, simple view, soul, mereological simplicity. 1 Introduction The simple approach to personal identity – the label used in the literature is 'the simple view' – is a family of theories of personal identity loosely connected by various philosophical presuppositions, principles, and a general theoretical stance. However, despite several attempts to find a unique or common thread that connects all these features, the variety of such theories may suggest only a loose and theoretically irrelevant resemblance among them.1 The problem of finding a unifying feature among these theories has been specified by Eric Olson as the task of answering the following questions: "What proposition is it that friends of complex views accept and friends of the simple view deny? What do you have to believe in order to accept a complex view, and what belief (or lack of belief) characterizes the simple view?" (Olson, 2012, p. 44).2 There are at least two strategies to distinguish simple from complex theories of personal identity, one that appeals to conceptual or theoretical features of the views at issue, e.g., versions of the simple approach sometimes hold that the concept of personal identity is not further analysable or reducible to simpler concepts 1 See (Olson, 2012; Hummel, 2017). I use the label 'the simple approach' for what is currently called 'the simple view'. An approach to X is one or a family of more or less specific ways in which a theory or view about X is. 2 In what follows I focus mostly on those parts of the above questions involving the simple view. i i "Libro" - 2019/4/10 - 8:25 - page 348 - #340 i i i i i i 348 ANDREA SAUCHELLI or relations, and another that focuses on the metaphysical nature of the entities, properties, or relations on which personal identity is supposed to be grounded or to depend upon.3 As other philosophers have already discussed a series of problems related to the first type of strategy, I will not repeat their arguments here.4 Rather, I will focus on a strategy to define the simple approach that is based on the metaphysical nature of the entities, properties, or relations used to analyse the relation of personal identity (Section 1). In the remainder of this essay, I outline how my way of defining the simple approach is applied to the various claims associated with classical and contemporary (alleged) simple theories (Section 2) and then why distinguishing simple from complex approaches along the above lines can still have some theoretical merit (Sections 2 and 3). The main structure of the argument in favour of the theoretical merit of my definition is that (i) such a definition allows me to draw a significant number of useful distinctions between conceptually different claims about personal identity (this point is discussed in Section 2), and (ii) it helps bring out a variety of other theses that supporters of the simple approach are likely to endorse in virtue of the simplicity of the entity used to analyse personal identity and which are part of what I call the simple-soul stance (this claim is discussed in Section 3). For instance, a belief in a simple entity as the metaphysical foundation of personal identity is generally associated with a theoretical stance adopted by several theistic thinkers. 2 The characterisation of the simple approach My understanding of the simple approach involves the idea that versions of this approach, i.e., theories that properly belong to this family of theories, to personal identity generally make both a grounding and a criterial claim.5 More specifically, a supporter of the simple approach qua supporter of the simple approach should say, on reflection, that her account involves a claim to the effect that the holding of the relation of personal identity depends on the holding of something else (not dependent on the holding of the relation of personal identity), where this dependence may be further specified as logical or, better, metaphysical. In addition, a supporter of (one version of) the simple approach should also say (on reflection) that her account involves a useful criterion or useful criteria (i.e., a set of non3 An attempt of the first type is (Noonan, 2011). Parfit (1984/6/7) seems to propose a mixed strategy, especially when he discusses non-reductionism and the simple view together. See also (Parfit, 1999). 4 See (Noonan, 2011; Olson, 2012; Zimmerman, 2012; Duncan, 2014; Hummel, 2017). 5 Pace (Gasser and Stefan, 2012, p. 3). i i "Libro" - 2019/4/10 - 8:25 - page 349 - #341 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY 349 trivial necessary and sufficient conditions) that figure in a bi-conditional having the following form: "Necessarily, if x is a human person at time t and y exists at another time t*, x = y if and only if [. . . ]" (Olson, 2012, p. 47). On my definition, versions of the simple approach are those theories that share at least the following claim: personal identity is a relation that essentially depends on a mereologically simple (i.e., impartite, or not composed of proper parts) entity that (I) is essentially related to our mental properties and that, in virtue of this relation, (II) has a series of features (including its existence) directly (e.g., by introspection) or indirectly knowable. Clause (I) captures the idea that the mereologically simple entity upon which personal identity depends is generally taken to be the subject of our metal states and/or as being metaphysically necessary for such mental states.6 The clause "has a series of features (including its existence) directly (e.g., by introspection) or indirectly knowable" is supposed to express neutrality with respect to various theories of the soul (i.e., the mereologically simple entity generally taken to ground personal identity by those who accept the simple approach). In particular, these theories may hold that: a. we can know directly the nature of our soul or that it exists (e.g., by introspection and/or acquaintance), a. we can know indirectly the nature of our soul and/or that it exists (e.g., by deduction from introspection or by deduction or reflection on the nature of the mental). Also, some theories may hold that the soul is an entity the existence of which we should postulate for explanatory reasons (e.g., to explain the phenomenological aspects of our mental states). This characterisation may sound counterintuitive (or just plainly wrong) to those who associate the simple approach with the claim that personal identity is not analysable – perhaps because the concept of personal identity is taken to be conceptually primitive. This idea is often accompanied by the point that 'there are no (informative) criteria of personal identity'. In reply, I think that we should distinguish this latter no-criterialist approach from the simple approach. As I will show in what follows, these two ideas are conceptually different. One last point: my definition is revisionary in the sense that it is supposed to tell us how the simple approach should be defined. So, my definition is not meant to capture all of the ways in which the simple approach is currently understood/specified. Rather, the idea is that by defining the simple approach the 6 See (Varzi, 2016) for an introduction to mereology. A simple entity is there defined as follows. "Mereologically, an atom (or "simple") is an entity with no proper parts, regardless of whether it is point-like or has spatial (and/or temporal) extension [. . . ]". i i "Libro" - 2019/4/10 - 8:25 - page 350 - #342 i i i i i i 350 ANDREA SAUCHELLI way I propose, we are able to make a series of interesting conceptual distinctions that classify most of the theories currently described as simple as belonging to the simple approach. 3 Applications of the characterisation Historically, versions of the simple view/approach have been theories that involve a soul criterion of personal identity or theories that have emphasised certain religious and practical aspects of the notion of personhood. I take this to be one requirement for a successful definition of the simple view: being able to account for at least this way of classifying the simple approach. My definition correctly classifies as belonging to the simple approach all those theories according to which personal identity over time depends on a simple soul. More specifically, my definition correctly identifies Plato's (in the Phaedo), (certain versions of) Augustine's, Descartes', and Richard Swinburne's accounts of the soul, as theories that can ground or are versions of the simple approach. So, Cartesian Egos – simple and conscious entities – and Platonic souls – immortal entities that share some of the metaphysical features of the Forms – are entities that make theories of personal identity employing them as simple. Now, there are conceptions of the soul according to which the soul is composite, i.e., according to which the soul is composed of different proper parts. My characterisation classifies theories of personal identity based on such a conception as not simple. The following list of claims loosely associated with the simple approach in the literature will help us understand how my definition works and the kind of conceptual distinctions we can draw by adopting it: • (Metaphysical further fact): Personal identity depends on a further fact, where this fact is further with respect to psychological or physical (biological) facts. • (Anti-criterialism): There are no criteria of personal identity. • (Brute fact): Personal identity holds only in virtue of itself, or the holding of personal identity is a brute fact. • (Determinacy about personal identity): There is always a yes/no answer with respect to certain puzzling thought experiments involving borderline cases of personal identity over time (e.g., brain transplant scenarios). i i "Libro" - 2019/4/10 - 8:25 - page 351 - #343 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY 351 • (Epistemicism about personal identity): There is always a yes/no answer with respect to certain puzzling thought experiments involving borderline cases of personal identity over time (e.g., brain transplant scenarios) and it may be the case that such an answer cannot be known/is unknowable. • (Conceptual simplicity): The concept of personal identity is not further analysable; that is, there are no simpler concepts in terms of which the concept of personal identity can be analysed or understood. • (Circularity): The relation of personal identity cannot be defined/analysed in terms of conditions the applicability of which does not already depend on the concept/relation of personal identity.7 My characterisation provides the basis for an explanation as to why the metaphysical further fact claim can be connected (as it has been) to simple theories of personal identity: if the further fact in question is that a simple soul exists and, given a theory of personal identity based on such a soul, the theory of personal identity at issue would count as simple. My characterisation provides the basis for distinguishing anti-criterialism from the simple approach. This is a theoretical virtue since a simple-soul approach does seem to provide a criterion of personal identity, whilst the anti-criterialist claims that this cannot be done. The point can be rephrased in the following way. Since in the history of (Western) philosophy a series of theories of personal identity based on a simple soul have been proposed and such theories have been understood as providing a criterion for personal identity, it is theoretically useful to distinguish these theories from anti-criterialism. In addition, such a criterion, or, better, the identity conditions over time of the entity that is supposed to ground the relation of personal identity (i.e., a simple soul), are not trivial. So, conflating the two claims that characterise anti-criterialism and simple-soul views is a conceptual confusion, similar to the conflation of the simple view and mind-body dualism. A simple-soul theory of personal identity should also be distinguished from a brute fact theory. In fact, a simple-soul theorist does not have to claim that the concept of a soul is not further analysable or that we cannot provide criteria of identity for the continuity over time of the same soul. Quite the contrary, many advocates of the simple-soul approach do provide such criteria: for instance, they 7 It is not always clear in the current literature whether "analysis of personal identity" is intended to refer to a metaphysical analysis, conceptual analysis, semantic analysis, or something else. In what follows, when I use the term "relation", I signal that the analysis at issue is metaphysical, whilst "notion" and "concept" stand for a conceptual analysis. i i "Libro" - 2019/4/10 - 8:25 - page 352 - #344 i i i i i i 352 ANDREA SAUCHELLI claim that the same soul continues through time iff a soul maintains the disposition to have or generate consciousness or some mental states. Theories such as Swinburne's, which claims that personal identity holds in virtue of the persistence of an essentially conscious soul (or, at least, of a soul that is essentially capable of being conscious), are not properly classified as brute fact theories: after all, such theories provide non-trivial conditions for the holding of personal identity and of soul-continuity through time that are not entailed by the concept of personhood. In short, my characterisation of the simple approach does not entail that simple theories are conceptually simple. In fact, the synchronic and diachronic conditions of identity of the simple entity in question may be conceptually complex, that is, different concepts can be used to characterise the nature of the metaphysically simple entity in question. Why should we hold that a theory of personal identity that depends on some relation be classified as simple? The simple approach has been understood also as that family of theories according to which personal identity consists in anything but itself. Consisting in anything but itself excludes that the holding of some other relation constitutes (or grounds) the relation of personal identity.8 My reply is that we should distinguish between this form of anti-criterialism/brute view and theories of personal identity based on a soul-criterion. Again, philosophers such as Swinburne claim that personal identity depends on sameness of soul so, on this view, the claim 'personal identity consists in anything but itself' can be true iff soul identity is identical with personal identity (i.e., iff they are the same relation). However, many theorists (including Swinburne, I suppose) would not claim that personal identity is (identical to) soul identity – the 'is' in between the two relata is rather generally taken to express a relation of metaphysical dependence. In particular, what they mean is that the relation of personal identity depends on identity of soul. The epistemicist condition on personal identity is frequently associated with the simple view and is fully compatible with my definition: the simple entity on which personal identity is allegedly based can be in principle unknowable – and this is the role of the epistemological clause included in my definition. Such unknowability can be explained in virtue of the simplicity of what has to be known, that is, because of its 'otherness' with respect to the nature of those things to which our perceptual capacities have been attuned. In a Platonic (and, admittedly, old-) fashion way, we might claim that such capacities are in fact generally involved in 8 The literature on metaphysical grounding is growing exponentially. See (Bliss and Trogdon, 2014) for an introduction. My definition is intended to be neutral with respect to the main views in the area. i i "Libro" - 2019/4/10 - 8:25 - page 353 - #345 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY 353 the perception of a complex (i.e., composite) reality. More should be said in this regard, but it would lead us too far from the main issue discussed in this paper.9 The simple approach is sometimes associated with the idea that certain nonsimple analyses of personal identity are circular – which is usually accompanied by the further claim that a characterising feature of the simple approach is that theories that belong to this family embrace such a circularity or that circularity does not constitute a problem for these theories. More specifically, several supporters of (what is called) the simple view have argued that generic psychological accounts of personal identity are irremediably circular. The reason is that some of the concepts used in these theories to analyse personal identity already presuppose the concept of personal identity. In addition, such a circularity is taken to undermine at least the claim, ascribed to supporters of some psychological theories, that the relation of personal identity can be fully analysed in terms of simpler notions/relations.10 The point is based on the idea that a necessary condition for, say, a memory connection to be proper (i.e., one memory connection that, along with a sufficient number of other connections, can properly sustain personal identity through time) is the identity between the experiencer and the person who later remembers such experiences. My concern here is not to evaluate these arguments but their relevance to my characterisation: since it seems that many supporters of the simple approach consider this argumentative strategy as providing reasons to believe their views, my characterisation should be at least compatible with such a line of reasoning. Now, according to my definition, the simple approach may include theories according to which the synchronic/diachronic identity conditions of the simple entity grounding personal identity over time can be specified independently of the relation of personal identity. Certain versions of the simple approach may make such a claim, which would then carry with it the burden of proving that personal identity can be properly and completely analysed solely in terms of a simple entity or soul without using the notion of personal identity. Other versions of the simple approach may be specified as theories that do not aim at providing a reduction or conceptual analysis of the concept of personal identity in terms of simpler notions. Still, I think that it is conceptually useful to distinguish the idea that analysing personal identity in terms of certain psychological connections is irremediably circular from theories according to which it is simple souls that ground personal identity. In this section, I have shown that my definition in terms of a mereologically simple entity is useful because it highlights the difference between a series of var9 See for instance (Fine, 1999; Benson, 2006, in particular Part II). 10 See (Slors, 2001; Roache, 2006) for further discussion. i i "Libro" - 2019/4/10 - 8:25 - page 354 - #346 i i i i i i 354 ANDREA SAUCHELLI ious conceptual claims about personal identity generally lumped together under the heading of the 'simple view'. In the next section, I offer further reasons to believe that distinguishing theories on the basis of such a mereologically simple entity is theoretically useful. 4 The simple-soul stance The main purpose of this section is to provide further reasons to believe in the theoretical usefulness of my previous definition in terms of a mereologically simple entity. My strategy in this section is (1) to describe some of the features that a simple entity is supposed to have, be compatible with, or imply qua simple entity; (2) to show that such features are generally associated with some important historical and contemporary versions of the simple approach; (3) to highlight the typical theoretical stance that supporters of the simple approach tend to have, i.e., the type of concerns or theoretical background that supporters of this family of views generally have. I understand the notion of a stance as including: [. . . ] a 'mode of engagement' – a way of going about things – which has an effect on how its possessor forms beliefs, inquires, and even experiences 'the world'. In other words, each stance involves a 'posture', which partially determines how, and when, shifts to other stances can, and do, occur. Some modes of engagement are conservative and serve to limit change, whereas others are more liberal and serve to encourage it (Rowbottom and Bueno, 2011, p. 7).11 In addition, a stance involves certain beliefs and theses supporting such a mode of engagement. Now, the adoption of a simple approach signals the likely acceptance of a theoretical stance conducive to or including a series of other claims. To the degree that it is theoretically interesting to recognise and underline such claims, my definition is theoretically valuable. A disclaimer: I do not claim that all of the features or ideas associated with the stance at issue do logically entail each other. My claim is weaker: generally – and for a variety of reasons – supporters of the simple approach have adopted a stance, some of the main claims of which are frequently taken to support each other. In particular, the simplicity of the soul is one of the distinguishing traits of a long tradition of theorising not only about 11 The notion of a stance has been recently discussed in the context of philosophy of science. See (Rowbottom and Bueno, 2011) for further references. i i "Libro" - 2019/4/10 - 8:25 - page 355 - #347 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY 355 personal identity but also on our nature. Such a tradition is also at the basis of contemporary developments of dualist and soul-based criteria of personal identity and our nature.12 Such developments in Western thought can be traced back at least to Plato: for instance, the idea that the soul is a simple substance plays a crucial role in the Phaedo.13 In particular, he (or, at least, the implied narrator of the dialogue or Socrates) maintains that the soul (soulPlatonic-Phaedo) is (i) partless or incomposite, (ii) immaterial, (iii) invariant, (iv) indissoluble, and (v) immortal.14 A theory of personal identity based on soulPlatonic-Phaedo can be formulated as follows: (SoulPlatonic-Phaedo Theory of the Metaphysical Foundation of Personal Identity): For all t, P at t1 is one and the same person as Q at t2 iff and because P's soulPlatonic-Phaedo at t1 = Q's soulPlatonic-Phaedo at t2. In the (modally stronger) form used at the beginning of this essay: Necessarily, if x is a human person at time t and y exists at another time t*, x = y if and only if x's soulPlatonic-Phaedo is the same soul as y's soulPlatonic-Phaedo. The above theory is substantially similar to the following summary of Swinburne's theory – a theory still currently proposed and discussed:15 (Swinburne's Dualistic Soulmind Theory of the Metaphysical Foundation of Personal Identity): For all t, where P and Q are each essentially a soulmind, P at t1 is one and the same person as Q at t2 iff P-soulmind at t1 = Q-soulmind at t2, provided that if t1 6= t2 then the conditions that allowed the soulmind to function properly at t1 are realised at t2. For instance, if the soulmind requires a body to function, then the soulmind must inform a body with mind-related equivalent functions. In the (modally stronger) form used at the beginning of this essay: 12 See (Sauchelli, 2018, Ch. 1) for an introduction to some of the main thinkers adopting this approach. 13 See (Apolloni, 1996; Bostock, 1986; Gerson, 2003). 14 These properties are argued for in many passages, for instance in the affinity argument (78b-84b). 15 The formulation of Swinburne's theory in the main text is my rational reconstruction of what he claims in (Swinburne, 1984, 2009, 2013). i i "Libro" - 2019/4/10 - 8:25 - page 356 - #348 i i i i i i 356 ANDREA SAUCHELLI Necessarily, if x is a human person at time t and y exists at another time t*, x = y if and only if x's soulmind = y's soulmind. According to the Phaedo, two key features that souls are supposed to have in virtue of their simplicity (or lack of proper parts) are their indissolubility and immortality. Although the two concepts are not equivalent, the metaphysical fact of the soul's simplicity can be taken to provide the metaphysical basis for explaining why souls are immortal, e.g., in Plato, composite objects were taken to be, at least at a metaphysical level, divisible and thus perishable. Impartite entities cannot be further divided, so they are not perishable in the same way in which composite objects are. The idea according to which souls are simple is what, on this account, grounds or explains their immortality, or at least, their simplicity can be taken to be a necessary condition for immortality.16 Now, the point is not that all of the supporters of one version of the simple soul approach also believe that the soul is immortal because of its simplicity. Rather, the point is that belief in the simplicity of the soul is generally a part of a theoretical stance – frequently associated with certain theistic thinkers – that is favourable to the acceptance of the immortality of the soul (but not necessarily so). I take it that the simple-soul stance under discussion here is not equivalent to an approach to personal identity – hence it is discussed in a separate section – also because a theory of personal identity as such does not entail a theory of our nature.17 A theory of our nature is supposed to tell us what we are, and some such theories (e.g., animalism) hold that we are not necessarily persons – in other words, the thesis that we are essentially persons is controversial. Still, a theory of our nature according to which we are essentially human animals may in principle agree with a theory of personal identity according to which persons persist qua persons only in virtue of, say, certain psychological connections between their temporal stages. A simple-soul stance would include a tendency to regard our nature, and not only the identity conditions of persons, as being connected to the nature of souls. In particular, a simple-soul stance may include the theory, sometimes called simple dualism, according to which we are essentially simple souls. Other theoretical possibilities include compound dualism ('we are essentially a compound of body and simple soul') and non-modal versions of the previous theories (e.g., 'we are simple souls, but not essentially so'). Again, distinguishing theories on the basis of a mereologically simple entity contributes to classifying the above theories under the same stance. 16 This connection has been vigorously disputed by, among others, Kant in his Critique. Swinburne rejects this argument as well. 17 See (Olson, 2007) for an introduction to personal ontology. i i "Libro" - 2019/4/10 - 8:25 - page 357 - #349 i i i i i i THE SIMPLICITY OF THE SIMPLE APPROACH TO PERSONAL IDENTITY 357 Another line of reasoning goes as follows. There is a connection between thinkers such as Plato, Augustine, Descartes, and Swinburne: a belief in the simplicity of the soul and a tendency to see what grounds personal identity as related to the divine.18 More specifically, the simplicity of the soul can be seen as conducive to an explanation of its divine or supernatural origin: as God or the Forms are sometimes taken to be simple, souls also have this (alleged) 'mark of the divine', which distinguishes them from the perishable and changing reality. And highlighting this feature in theories of personal identity is theoretically interesting. 5 Conclusions Isolating a family of theories based on the idea that the relation of personal identity depends upon (the continuity of) a simple entity is theoretically useful. In Section 2, I argued that such a distinction provides the theoretical basis to draw and motivate a series of useful theoretical distinctions among theories of personal identity (and of our nature). In Section 3, I claimed that the definition is useful also because a belief in the simplicity of the soul – one of the main characterising features of my definition – seems to be part of a theoretical stance adopted by various thinkers favourably inclined to theism and to a series of other related doctrines. Such a stance is not equivalent to a theory of personal identity because it may include, among other things, a series of claims about our nature. References Apolloni, D. (1996). Plato's affinity argument for the immortality of the soul. Journal of the History of Philosophy, 34(1): 5–32. Bliss, R and Trogdon, K. (2014). Metaphysical grounding. In Stanford Encylopedia of Philosophy. Retrieved from https://plato.stanford.edu/entries/grounding/ Benson, H., editor. (2006). A Companion to Plato. Blackwell, Oxford. Bostock, D. (1986). Plato's Phaedo. Clarendon Press, Oxford. Broadie, S. (2001). Soul and body in Plato and Descartes. Proceedings of the Aristotelian Society, 101:295–308. 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