The relationship between smell and politics could appear obscure; and yet, when it comes to smell, questions about freedom and constriction, social and ontological mingling or distinctions, clearly arise. In this paper, I will especially focus on the domain of food as a clear example for describing some of the political ambivalences characterizing the sense of smell. The aim is to pave the way for a more detailed ‘sociopolitical aesthetics of smell’ to come. I will stress epistemological and social features (...) of odors in order to highlight their ambivalence in knowledge and community life. Perceivers and odors will emerge as mingled bodies, highlighting an ongoing process of material as well as emotional affection. Moreover, I will present some relevant examples of smell as social status symbols in relation to the aesthetic values linked to class hierarchy. Consumerism and scented goods will be lastly discussed in order to shade light on contemporary perceptual phenomena and their role in the socioeconomic dimension. (shrink)

Bewildering features of modern physics, such as relativistic space-time structure and the peculiarities of so-called quantum statistics, challenge traditional ways of conceiving of objects in space and time. Interpreting Bodies brings together essays by leading philosophers and scientists to provide a unique overview of the implications of such physical theories for questions about the nature of objects. The collection combines classic articles by Max Born, Werner Heisenberg, Hans Reichenbach, and Erwin Schrodinger with recent contributions, including several papers that have never (...) before been published. -/- The book focuses on the microphysical objects that are at the heart of quantum physics and addresses issues central to both the "foundational" and the philosophical debates about objects. Contributors explore three subjects in particular: how to identify a physical object as an individual, the notion of invariance with respect to determining what objects are or could be, and how to relate objective and measurable properties to a physical entity. The papers cover traditional philosophical topics, common-sense questions, and technical matters in a consistently clear and rigorous fashion, illuminating some of the most perplexing problems in modern physics and the philosophy of science. (shrink)

In recent years, a ''change in attitude'' in particle physics has led to our understanding current quantum field theories as effective field theories (EFTs). The present paper is concerned with the significance of this EFT approach, especially from the viewpoint of the debate on reductionism in science. In particular, I shall show how EFTs provide a new and interesting case study in current philosophical discussion on reduction, emergence, and inter-level relationships in general.

A draft version of Chapter 11 of the edited volume 'Interpreting Bodies. Classical and Quantum Objects in Modern Physics',. The Chapter is devoted to illustrating the group-theoretic approach to the issue of physical objects. In particular, the Chapter discusses the group-theoretic constitution of classical and quantum particles in the nonrelativistic case.

In recent years, a change in attitude in particle physics has led to our understanding current quantum field theories as effective field theories. The present paper is concerned with the significance of this EFT approach, especially from the viewpoint of the debate on reductionism in science. In particular, it is a purpose of this paper to clarify how EFTs may provide an interesting case-study in current philosophical discussion on reduction, emergence and inter-level relationships in general.

Slurs have become a big topic of discussion both in philosophy and in linguistics. Slurs are usually characterised as pejorative terms, co-extensional with other, neutral, terms referring to ethnic or social groups. However, slurs are not the only ethnic/social words with pejorative senses. Our aim in this paper is to introduce a different kind of pejoratives, which we will call “ethnic/social terms used as insults”, as exemplified in Spanish, though present in many other languages and mostly absent in English. These (...) are ethnic terms like gitano, ‘Romani’, which can have an extensional and neutral use, but also a pejorative meaning building on a negative stereotypical representation of the Romani community. (shrink)

This open access book features essays written by philosophers, biologists, ecologists and conservation scientists facing the current biodiversity crisis. Despite increasing communication, accelerating policy and management responses, and notwithstanding improving ecosystem assessment and endangered species knowledge, conserving biodiversity continues to be more a concern than an accomplished task. Why is it so?The overexploitation of natural resources by our species is a frequently recognised factor, while the short-term economic interests of governments and stakeholders typically clash with the burdens that implementing conservation (...) actions imply. But this is not the whole story. This book develops a different perspective on the problem by exploring the conceptual challenges and practical defiance posed by conserving biodiversity, namely: on the one hand, the difficulties in defining what biodiversity is and characterizing that “thing” to which the word ‘biodiversity’ refers to; on the other hand, the reasons why assessing biodiversity and putting in place effective conservation actions is arduous. (shrink)

Weak/strong duality is usually accompanied by what seems a puzzling ontological feature: the fact that under this kind of duality what is viewed as 'elementary' in one description gets mapped to what is viewed as 'composite' in the dual description. This paper investigates the meaning of this apparent 'particle democracy', as it has been called, by adopting an historical approach. The aim is to clarify the nature of the correspondence between 'dual particles' in the light of an historical analysis of (...) the developments of the idea of weak/strong duality, starting with Dirac's electric-magnetic duality and its successive generalizations in the context of field theory, to arrive at its first extension to string theory. This analysis is then used as evidential basis for discussing the 'elementary/composite' divide and, after taking another historical detour by analysing an instructive analogy case, drawing some conclusions on the particle-democracy issue. (shrink)

Is there more that one "Curie's principle"? How far are different formulations legitimate? What are the aspects that make it so scientifically fruitful, independently of how it is formulated? The paper is devoted to exploring these questions. We start with illustrating Curie's original 1894 article and his focus. Then, we consider the way that the discussion of the principle took shape from early commentators to its modern form. We say why we think that the modern focus on the inter-state version (...) of the principle loses sight of some of the most interesting significant applications of the principle. Finally, we address criticism of the principle put forward by Norton and purported counterexamples due to Roberts. (shrink)

This is the first of two papers concerned with the philosophical significance of dualities as applied in recent fundamental physics. The general idea is that, for its peculiarity, this ‘new’ ingredient in theory construction can open unexpected perspectives in the current philosophical reflection on contemporary physics. In particular, today’s physical dualities represent an unusual type of intertheory relation, the meaning of which deserves to be investigated. The aim is to show how discussing this point brings into play, at the same (...) time, what is intended by a 'theory’ and in which sense dualities are to be considered 'symmetries'. This paper is introductory and focusses on the first form of duality explicitly applied in twentieth century physics, that is electromagnetic duality as discussed in Dirac’s theory of magnetic poles. The extension of electromagnetic duality in the context of quantum field theory and string theory is explored in a forthcoming companion paper. (shrink)

This comment considers the Italian Law 194 on abortion forty years after its approval in 1978 and it focuses on how its meaning has emerged as a result of its interpretation and application over that forty-year period.

This paper addresses the question as to whether the methodology followed in building/assessing string theory can be considered scientific in the same sense, say, that the methodology followed in building/assessing the Standard Model of particle physics is scientific, by focussing on the "founding" period of the theory. More precisely, its aim is to argue for a positive answer to the above question – there is no real change of scientific status in the way of proceeding and reasoning in fundamental physical (...) research – in the light of a historical analysis of the early developments of the string theoretical framework. (shrink)

After having reconstructed a minimal biological characterisation of species, we endorse an “empirical approach” based on the idea that it is the peculiar evolutionary history of the species at issue—its peculiar origination process, its peculiar metapopulation structure and the peculiar mixture and strength of homeostatic processes vis à vis heterostatic ones—that determines species’ identity at a time and through time. We then explore the consequences of the acceptance of the empirical approach in settling the individuals versus kinds dispute. In particular, (...) while conceptual arguments have been proposed to show that species can be equally treated as individuals and kinds because mereology’s and set-theory’s languages are inter-translatable, we advance instead a causal argument to sustain the claim that each species is both a kind and an individual. (shrink)

The relevance of symmetry to today's physics is a widely acknowledged fact. A significant part of recent physical inquiry – especially the physics concerned with investigating the fundamentalbuilding blocks of nature – is grounded on symmetry principles andtheir many and far-reaching consequences. But where these symmetries come from and what their real meaning is are open questions, at the center of a developing debate among physicists and philosophers of science. To tackle the problems arising in considering the symmetry issue is (...) the main purpose of this paper. Starting with briefly recalling the bases for the discussion – how symmetry enters and operates in physics, its special effectiveness in the quantum domain and the many relevant functions it performs (Sections 1–3), the paper then focus on the general interpretative questions that arise and the sorts of answers that have been given (Section 4). (shrink)

We argue that dualities offer new possibilities for relating fundamentality, levels, and emergence. Namely, dualities often relate two theories whose hierarchies of levels are inverted relative to each other, and so allow for new fundamentality relations, as well as for epistemic emergence. We find that the direction of emergence typically found in these cases is opposite to the direction of emergence followed in the standard accounts. Namely, the standard emergence direction is that of decreasing fundamentality: there is emergence of less (...) fundamental, high-level entities, out of more fundamental, low-level entities. But in cases of duality, a more fundamental entity can emerge out of a less fundamental one. This possibility can be traced back to the existence of different classical limits in quantum field theories and string theories. (shrink)

This paper is concerned with the problem of the validity of Leibniz's principle of the identity of indiscernibles in physics. After briefly surveying how the question is currently discussed in recent literature and which is the actual meaning of the principle for what concerns physics, we address the question of the physical validity of Leibniz's principle in terms of the existence of a sufficient number of naming predicates in the formal language of physics. This approach allows us to obtain in (...) a formal way the result that a principle of the identity of indiscernibles can be justified in the domain of classical physics, while this is not the case in the domain of quantum physics. (shrink)

Nella ricerca antropologica, la distinzione “natura/cultura” è considerata una delle dicotomie di base che soggiacciono – nel corso della storia – ai diversi modelli del mondo. Nei termini di questa distinzione ci orientiamo nell’ambiente che ci circonda, tracciamo distinzioni metafisiche, formuliamo giudizi di valore. Eppure, tanto questa opposizione è intuitiva e di immediata comprensione, tanto diventa sfuggente non appena si tenti di individuare dove sia il confine che la definisce, e di...

The concept of nature in Western thought has been informed by the assumption of a categorical distinction between natural and artificial entities, which goes back to John Stuart Mill or even Aristotle. Such a way of articulating the natural/artificial distinction has proven unfit for conservation purposes mainly because of the extent and the pervasiveness of human activities that would leave no nature left to be conserved, and alternative views have been advanced. In this contribution, after arguing for the importance of (...) the concept of naturalness as a guide for conservation, I will try to provide an account of the natural/artificial distinction suited to contemporary conservation framing. Focusing on a particular kind of objects that I suggest to name “environmental objects”, I propose and defend the view of “naturalness as independence” according to which the more or less an environmental object's identity conditions and survival depend on human intervention, the more or less that object is artificial or natural, respectively. According to this view, conserving environmental objects will equate to maintaining or improving their naturalness or even originating artificial objects that may become new natural objects. This view has the advantage, on the one hand, of providing a rationale for a distinction which is not only part of how people think, but also pervasive in conservation practices and policies and, on the other hand, of accounting for the global pervasiveness of human intervention in the so-called natural world. (shrink)

Visuo-motor adaptation to optical prisms displacing the visual scene (prism adaptation, PA) is a method used for investigating visuomotor plasticity in healthy individuals and, in clinical settings, for the rehabilitation of unilateral spatial neglect. In the standard paradigm, the adaptation phase involves repeated pointings to visual targets, while wearing optical prisms displacing the visual scene laterally. Here we explored differences in PA, and its aftereffects (AEs), as related to the sensory modality of the target. Visual, auditory, and multisensory - audio-visual (...) - targets in the adaptation phase were used, while participants wore prisms displacing the visual field rightwards by 10◦. Proprioceptive, visual, visual-proprioceptive, auditory-proprioceptive straight-ahead shifts were measured. Pointing to auditory and to audio-visual targets in the adaptation phase produces proprioceptive, visual-proprioceptive, and auditory-proprioceptive AEs, as the typical visual targets did. This finding reveals that cross-modal plasticity effects involve both the auditory and the visual modality, and their interactions (Experiment 1). Even a shortened PA phase, requiring only 24 pointings to visual and audio-visual targets (Experiment 2), is sufficient to bring about AEs, as compared to the standard 92-pointings procedure. Finally, pointings to auditory targets cause AEs, although PA with a reduced number of pointings (24) to auditory targets brings about smaller AEs, as compared to the 92-pointings procedure (Experiment 3). Together, results from the three experiments extend to the auditory modality the sensorimotor plasticity underlying the typical AEs produced by PA to visual targets. Importantly, PA to auditory targets appears characterized by less accurate pointings and error correction, suggesting that the auditory component of the PA process may be less central to the building up of the AEs, than the sensorimotor pointing activity per se. These findings highlight both the effectiveness of a reduced number of pointings for bringing about AEs, and the possibility of inducing PA with auditory targets, which may be used as a compensatory route in patients with visual deficits. (shrink)

RESUMENInvorme bibliográfico sobre Baltasar gracián que incluye las referencias de los años 1996-1998. Revisa y actualiza repertorios y bibliografías anteriores publicadas por la misma autora.GRACIÁN-FILOSOFÍA ESPAÑOLA-BARROCOABSTRACTBibliographical report on Baltasar Gracian that includes the references from 1996 to 1998. it revises and updates previous bibliographies published by the same author.KEYWORDSGRACIAN-SPANISH PHILOSOPHY.BARROQUE.

The essay focuses on the Italian evolutionist Tito Vignoli, whose work is the result of a fruitful contamination between philosophy, history of religion, linguistics, ethnography, anthropology, psychology, zoology and physiology. His most regarded book, Mito e scienza (1879), and some of his minor writings deal with the theory of myth, art and aesthetics in the new framework of Darwin's ideas.

In the context of astrophysical modeling at the solar system scale, we investigate the modalities implied by taking into account different levels of detail at which phenomena can be considered. In particular, by framing the analysis in terms of the how-possibly/how-actually distinction, we address the debated question as to whether the degree of plausibility is tightly linked to the degree of detail. On the grounds of concrete examples, we argue that, also in the astrophysical context examined, this is not necessarily (...) the case. (shrink)

¿Qué significa "fracasar" para un naturalista metodológico? ¿Está éste abocado al escepticismo, y es este un fracaso? Para responder a estas preguntas, realizaré (1) un análisis de lo que se considera "naturalismo" en Hume, desde el que analizaré (2) la crisis escéptica narrada en la conclusión del Libro I del Tratado. Allí defenderé que la metafórica utilizada, engarzada con el concepto de fracaso, permite dos lecturas: una que une necesariamente naturalismo metodológico y escepticismo mitigado, y otra que no. No obstante, (...) concluiré que en ambos casos se dibuja una misma experiencia de límite que permite construir ciencia y filosofía no-excepcionalistas. (shrink)

This paper reports an experiment that investigates interpretive distinctions between two different expressions of generalization in Spanish. In particular, our aim was to find out when the distinction between generic statements (GS) such as Tigers have stripes and universally quantified statements (UQS) such as All tigers have stripes was acquired in Spanish-speaking children of two different age groups (4/5-year-olds and 8/9-year-olds), and then compare these results with those of adults. The starting point of this research was the semantic distinction between (...) GS and UQS in that the former admit exceptions, unlike the latter. On the other hand, several authors have observed a Generic overgeneralization effect (GOG) consisting in allowing for UQS to be felicitous in the face of exceptions, thus proposing that this “error” stems from GS being defaults (simpler, more easily learned and processed). In the current paper we aimed to test the “Generics as Default” (GaD) hypothesis by comparing GS and UQS in three different age ranges. Our data show that, overall, the accuracy of GS is greater than the accuracy of UQS. Moreover, we also confirm a hypothesized interaction between age and NP type (GS vs UQS). Further, we present several data points that are not predicted by the GaD, including an observed decline in the accuracy of GS in the older group of children as well as in adults, and that children fail at rejecting statements that are not considered to be true generalizations. (shrink)

This is the final draft of Chapter 4 of the Volume 'The Birth of String Theory' edited by A. Cappelli, E. Castellani, F. Colomo, and P. Di Vecchia, Cambridge University Press, forthcoming.

Se leggiamo tra le righe del suo lavoro, possiamo scoprire che Varzi prende i mostri molto sul serio. Troviamo, per esempio, mostri mereologici frutto della composizione non ristretta, come l’entità costituita dalla metà sinistra di questa mela e dal bracciolo di quella poltrona.10 Oppure mostri topologici dai quali una teoria mereotopologica delle nicche deve rifuggire, come le curve riempispazio di Peano e Hilbert.11 O, ancora, mostri ontologici come l’antimateria;12 le entità “inesistenti” che, come si sa, non possono esistere, dato che (...) non ci sono cose che non esistono; e le entità “negative”: buchi, mancanze e omissioni, conferenze non date.13 In questo contributo, seguendo il suggerimento di Varzi, parlerò, appunto, di mostri, prendendo l’avvio da alcune creature che popolano il regno della finzione, per poi passare a trattare dei mostri che popolano il nostro mondo. Essendo poco lo spazio e molti i mostri, procederò dapprima proponendone una tassonomia – punto di partenza per ogni generalizzazione che si rispetti – e in seguito cercando di illustrare perché i mostri vadano presi sul serio in metafisica. È d’obbligo precisare che si tratterà di una tassonomia parziale e provvisoria, ma lo è altrettanto ricordare che le tassonomie, quelle biologiche in particolare, lo sono sempre, per due ragioni. In parte, perché la vita è in costante evoluzione, in parte perché le nostre conoscenze e decisioni condizionano la struttura e i contenuti dei nostri sistemi di categorie: basti pensare che la prima edizione del Systema naturae di Linneo contava undici pagine, mentre la tredicesima ben tremila, ripartite in sei volumi. Quando un tassonomo scopre un organismo che ritiene – dopo accurati esami comparativi – essere appartenente a una specie fino ad allora sconosciuta, ne deposita nella letteratura scientifica, insieme al nome binomiale (cioè il nome specifico, composto dall’indicazione del genere e della specie, come Homo sapiens), una descrizione in termini di caratteri fenetici. Quel token è chiamato tipo nomenclaturale, o esemplare-tipo, ed è il portatore del nome della specie di cui viene considerato tipo. Sulla falsariga della procedura appena descritta, riporterò la descrizione di alcuni tipi nomenclaturali per una tassonomia mostruosa che si baserà su tre criteri principali: (1) l’origine, (2) la costituzione genetica, (3) l’aspetto fenotipico. Prima di procedere, vorrei però sottolineare tre rispetti sotto i quali classificare mostri mitologici differisce dal classificare individui “ordinari”. Innanzitutto, nel caso dei mostri mitologici non è possibile, a causa del frequente intervento divino, ricorrere al criterio dell’interfecondità per stabilire se due mostri appartengono alla medesima specie. Ma d’altro canto, tale criterio, benché sia abbastanza affidabile per gli animali, non lo è affatto, per ragioni diverse dai mostri, per molte piante, alghe e funghi. Un’altra peculiarità da segnalare – di cui però non avremo modo di occuparci oltre – è che le entità mitologiche sono frequentemente soggette a trasformazioni sostanziali, mentre la nostra biologia sembra, aristotelicamente, escluderne la possibilità: una tigre non può trasformarsi in un canguro, pena la sua uscita dall’esistenza. Meno paradossalmente, una larva di mosca e la mosca adulta saranno considerate appartenenti alla medesima sorta – la mosca, appunto – benché dall’una all’altra non vi sia praticamente alcuna continuità materiale (nella metamorfosi la larva viene distrutta quasi completamente e l’adulto si genera a partire da pochi aggregati cellulari indifferenziati). Infine, nel caso dei mostri mitologici, parlerò più genericamente di “gruppo tassonomico” anziché di “specie” (e dunque il nome dei tipi nomenclaturali non sarà un nome binomiale) dal momento che, come diverrà chiaro nel corso della lettura, è proprio il concetto di “specie” come diverrà chiaro nel corso della lettura, è proprio il concetto di “specie” come articolazione naturale non oltrepassabile che i mostri che andiamo a classificare ci chiedono di mettere in discussione. (shrink)

Biological conservation has a long story, but what distinguishes Conservation Biology from previous conservation fields is its multidisciplinary scope and its character as a mission-oriented crisis discipline. These characteristics suggested the introduction of the metaphor of biological conservation as a sort of surgery. This paper is about the initial stages of such surgery. Firstly, some data about the so-called “Big Sixth”—the disease—will be presented together with some information about Conservation Biology—the surgeon. Then epistemic and epistemological difficulties in extinction assessment and (...) conservation prioritization, and triage in particular, will be pointed out. It will be argued that, while data deficiency arising from empirical and practical constraints can in principle be overcome, a different order of difficulties stems from the competition among several species concepts. In this case, it will be suggested that the extent of complications is of such significance to require a thorough re-assessment of the very nature of the patients, i.e., outside the metaphor, of the concept of species. (shrink)

Nel 2009, prendendo le mosse da articoli e libri pubblicati negli anni precedenti, Maurizio Ferraris proponeva la “documentalità”, una ontologia sociale che, a differenza della received view basata sull’intenzionalità collettiva, individuava il fondamento degli oggetti sociali negli atti iscritti. Prendendo come spunto due oggetti sociali tipicamente torinesi – il capoluogo piemontese è il luogo di nascita del filosofo – e cioè la casa automobilistica Fiat e l’Università di Torino, in questo breve saggio si discutono alcune tra le tesi che caratterizzano (...) una ontologia sociale siffatta. Particolare attenzione viene data alla tesi secondo cui l’identità di un oggetto sociale e la sua permanenza attraverso il tempo dipenderebbero dall’iscrizione che ne è alla base anziché, come per esempio nella posizione searliana, dall’oggetto fisico sottostante. Questa tesi, si sostiene, acquisisce particolare pregnanza nell’epoca del web, quell’acceleratore della documentalità, per dirla con le parole del filosofo, che ha la caratteristica di mostrare nella sua evidenza la struttura stessa della realtà sociale e, in tal modo, di diventare uno strumento per il cambiamento. Mettendo in luce la linea concettuale che unisce Documentalità (2009) con uno dei lavori più recenti di Ferraris, Mobilitazione totale (2015), si articola e si sostiene l’idea secondo cui il web svolge una duplice funzione. Da un lato, rivelare l’emergere della società dalla natura, riproducendo in tempi osservabili e in un ambiente monitorabile, quello di cui non è possibile essere spettatori diretti. Dall’altro, renderne evidente la struttura ultima che, appunto, è una struttura documentale. (shrink)

In questo contributo di introduzione al volume “Biodiversity” (Rivista di Estetica n. 59, 2015), dopo aver sottolineato il legame tra la realizzazione degli inventari biologici (le tassonomie) e lo studio della biodiversità, e la difficoltà di definire la biodiversità, prendo in esame tre diversi modi di intendere il valore della biodiversità. Oltre al valore etico ed estetico, oggetto rispettivamente di discipline relativamente recenti come l’etica ambientale e l’estetica ambientale, la biodiversità ha un valore economico, presente soprattutto nel cosiddetto approccio dei (...) servizi ecosistemici, dove la biodiversità è principalmente intesa nei termini dei servizi che gli ecosistemi possono offrire agli esseri umani presenti e futuri. (shrink)

An exchange of letters among proper names and natural-kind terms, dealing with various identity and individuation problems (rigid designation, use-mention ambiguities, translation) from their point of view.

The purpose of this paper is twofold: (1) to clarify Ludwig Wittgenstein’s thesis that colours possess logical structures, focusing on his ‘puzzle proposition’ that “there can be a bluish green but not a reddish green”, (2) to compare modeltheoretical and gametheoretical approaches to the colour exclusion problem. What is gained, then, is a new gametheoretical framework for the logic of ‘forbidden’ (e.g., reddish green and bluish yellow) colours. My larger aim is to discuss phenomenological principles of the demarcation of the (...) bounds of logic as formal ontology of abstract objects. (shrink)

Algorithmically driven online dating platforms today promise the ability to sort through relevant data and identify one’s ideal amorous matches effectively. Yet the appeal of technological and scientific solutions to the messy problem of finding partners is hardly new. This introduction to the Focus section “It’s a Match!” argues that the history of amorous matching has long been part and parcel of the history of science, in particular the social sciences. Taking matching as an “applied science of social harmony,” the (...) authors argue that concern over more reliable techniques for determining the suitability of partners has formed an essential part of both the maintenance of social order and the shaping of subjectivities, enabling discourses of informed choice and the rational management of the passions, while also reinforcing and subverting structures of age, gender, race, and sexuality. (shrink)

Kaum eine andere künstlerische Strategie prägte das Wertesystem der Kunst des 20. Jahrhunderts wie die Wiederholung. Sie lässt sich als wesentliches Moment ausmachen, neue Wahrnehmungsweisen zu ermöglichen, Kritik an Formen der Repräsentation zu üben und neuen Sinn zu produzieren. Der Band nimmt eine kritische Revision des Phänomens für die zeitgenössische Kunst vor und eröffnet anhand bildnerischer, skulpturaler, performativer, technisch-medialer wie auch kuratorischer Wiederholungen in der Kunst eine Perspektive auf die Wiederholung als Grundbegriff des Ästhetischen.

This paper is devoted to examining the relevance of Dirac's view on the use of transformation theory and invariants in modern physics --- as it emerges from his 1930 book on quantum mechanics as well as from his later work on singular theories and constraints --- to current reflections on the meaning of physical symmetries, especially gauge symmetries.