Peter Stemmer has developed an elegant and impressive theory of normativity and morality. In this article, I try to show that he does not achieve two goals he set for himself. First, his theory does not capture the categorical bindingness of moral demands, even in Stemmer’s own interpretation of categorical bindingness: it does not show that wemustfollow moral demands no matter what our personal goals and desires are. Second, just because it would be rational to establish (...) positive moralities in a hypothetical pre-moral scenario, it does not follow – and Stemmer does not establish – that only positive moralities that are in the interest of all members (and contain a prohibition on oppression) arelegitimate. For that reason, his contractarian theory collapses into relativism. (shrink)

The papers of this special issue are the outcome of a two-­‐day conference entitled “The Second-­‐Person Standpoint in Law and Morality,” that took place at the University of Vienna in March 2013 and was organized by the ERC Advanced Research Grant “Distortions of Normativity.” -/- The aim of the conference was to explore and discuss Stephen Darwall’s innovative and influential second-­‐personal account of foundational moral concepts such as „obligation“, „responsibility“, and „rights“, as developed in his book The Second-­‐Person Standpoint: Morality, (...) Respect, and Accountability (Harvard University Press 2006) and further elaborated in Morality, Authority and Law: Essays in Second-­‐Personal Ethics I and Honor, History, and Relationships: Essays in Second-­‐Personal Ethics II (both Oxford University Press 2013). -/- With the second-­‐person standpoint Darwall refers to the unique conceptual normative space that practical deliberators and agents occupy when they address claims and demands to one another (and to themselves). The very first sentence of Darwall’s examination of the second-­‐personal conceptual paradigm summarizes the gist of the argument succinctly when he claims that “the second-­‐person standpoint [is] the perspective that you and I take up when we make and acknowledge claims on one another’s conduct and will.” (Darwall 2006, 3) The Second-­‐Person Standpoint reminds us that this perspective has been ignored for much too long and that it better take centre stage in any philosophical analysis of moral phenomena, in order to yield a satisfying account of morality as a social institution. The negative part of Darwall’s strategy is to show that neither a purely first-­‐personal approach (represented by Kant and contemporary Kantians), nor a third-­‐personal state-­‐of-­‐affairs-­‐perspective (represented by most varieties of contemporary consequentialism) are capable of accounting for the categorical bindingness characteristic of moral obligation. The latter feat can only be accomplished, and this is the positive part of Darwall’s argument, when those second-­‐ personal normative “felicity conditions” and conceptual presuppositions are acknowledged and spelled out that are already presupposed in every instance of issuing (putatively valid) claims and demands. It is especially second-­‐personal competence and second-­‐personal authority that are the bedrock of these normative conceptual presuppositions, without which engaging in any meaningful address would be impossible. Kantians and utilitarians alike have neglected this critical dimension of the normative landscape. -/- In addition to working out an original conception of moral obligation, the first eight chapters of The Second-­‐Person Standpoint articulate this fundamental insight with respect to a variety of traditional projects in ethical theory such as developing accounts of moral responsibility, rights, dignity, and autonomy. In this context, special emphasis is to be awarded, on the one hand, to Darwall’s refreshing second-­‐personal interpretation of Strawson’s influential account of reactive attitudes and moral responsibility and, on the other, to his historically well-­‐informed reconstruction of Samuel Pufendorf’s often neglected version of an enlightened theistic voluntarism concerning moral authority. Darwall dedicates the second part of The Second-­‐Person Standpoint to the urgent question: how should one respond to the sceptical challenge that expresses utter indifference to the second-­‐person standpoint, including all its multifarious normative presuppositions and implications? What commits us to all this? It is at this point that Darwall, firstly, refines his criticisms of the Kantian, first-­‐personal, paradigm of normativity and emphasizes that only if one already incorporates the second-­‐personal conceptual apparatus into a Kantian analysis of moral obligation is the latter going to yield a convincing account. Secondly, and this certainly is one of the highlights of Darwall’s theory, the Second-­‐Person Standpoint employs themes from Fichte’s philosophy of right in order to strengthen the case for the inescapability of taking up the second-­‐person standpoint of moral obligation. In his contribution for this special issue Darwall further develops his diagnosis that Fichte’s thought offers in many respects a more promising, since more second-­‐personal, foundation of morality than, for example, Kant’s. -/- By now, the impact of Darwall’s second-­‐person standpoint theory has far transcended the confines of contemporary debates on moral obligation. Darwall has put to use the second-­‐personal apparatus to critical engagements with Joseph Raz’s theory of legal authority and Derek Parfit’s convergence arguments for his recent Triple Theory of moral wrongness. The constant theme that unifies all these diverse applications remains the one so impressively presented in The Second-­‐Person Standpoint: without paying attention to the “interdefinable” and “irreducible” circle of (four) foundational second-­‐ personal concepts (valid demand, practical authority, second-­‐personal reason, and accountability), neither superior epistemic status (Raz) nor the identification of optimific states of affairs (Parfit) are potent enough sources to generate anything close to the authority relationships that underlie the idea involved in obligating ourselves and one another. Given all of the above, it comes as no surprise that Darwall reserves his strongest sympathies for a specific ethical theory, namely contractualism. Our commitment to equal basic second-­‐personal authority, that Darwall arrives at through his Fichtean rectification of the Kantian project, leads him to the endorsement of a contractualist paradigm in the spirit of broadly Rawls and Scanlon. -/- . (shrink)

An ω-categorical supersimple group is finite-by-abelian-by-finite, and has finite SU-rank. Every definable subgroup is commensurable with an acl( $\emptyset$ )-definable subgroup. Every finitely based regular type in a CM-trivial ω-categorical simple theory is non-orthogonal to a type of SU-rank 1. In particular, a supersimple ω-categorical CM-trivial theory has finite SU-rank.

Downsizing has become a significant public issue that has not yet been significantly studied by business ethicists. It is proposed that reasonable social and psychological contracts bound the moral free space of managers contemplating downsizing; the degree of constraint is also dependent on the organization's resource munificence. A framework for considering the extent of managerial moral free space and implications thereof for managerial practice are offered.

A long series of conversations interweaving mathematical, historical and philosophical aspects of categoricity in model theory took place between the author and Saharon Shelah in 2016 and 2017. In this excerpt of that long conversation, we explore the relationship between explicit and implicit aspects of categoricity. We also discuss the connection with definability issues.

Many recent writers in the philosophy of mathematics have put great weight on the relative categoricity of the traditional axiomatizations of our foundational theories of arithmetic and set theory. Another great enterprise in contemporary philosophy of mathematics has been Wright's and Hale's project of founding mathematics on abstraction principles. In earlier work, it was noted that one traditional abstraction principle, namely Hume's Principle, had a certain relative categoricity property, which here we term natural relative categoricity. In this paper, we show (...) that most other abstraction principles are not naturally relatively categorical, so that there is in fact a large amount of incompatibility between these two recent trends in contemporary philosophy of mathematics. To better understand the precise demands of relative categoricity in the context of abstraction principles, we compare and contrast these constraints to stability-like acceptability criteria on abstraction principles, the Tarski-Sher logicality requirements on abstraction principles studied by Antonelli and Fine, and supervaluational ideas coming out of Hodes' work. (shrink)

After a short preface, the first of the three sections of this paper is devoted to historical and philosophic aspects of categoricity. The second section is a self-contained exposition, including detailed definitions, of a proof that every mathematical system whose domain is the closure of its set of distinguished individuals under its distinguished functions is categorically characterized by its induction principle together with its true atoms (atomic sentences and negations of atomic sentences). The third section deals with applications especially those (...) involving the distinction between characterizing a system and axiomatizing the truths of a system. (shrink)

Due to Gӧdel’s incompleteness results, the categoricity of a sufficiently rich mathematical theory and the semantic completeness of its underlying logic are two mutually exclusive ideals. For first- and second-order logics we obtain one of them with the cost of losing the other. In addition, in both these logics the rules of deduction for their quantifiers are non-categorical. In this paper I examine two recent arguments –Warren (2020), Murzi and Topey (2021)– for the idea that the natural deduction rules (...) for the first-order universal quantifier are categorical, i.e., they uniquely determine its semantic intended meaning. Both of them make use of McGee’s open-endedness requirement and the second one uses in addition Garson’s (2013) local models for defining the validity of these rules. I argue that the success of both these arguments is relative to their semantic or infinitary assumptions, which could be easily discharged if the introduction rule for the universal quantifier is taken to be an infinitary rule, i.e. non-compact. Consequently, I reconsider the use of the ω-rule and I show that the addition of the ω-rule to the standard formalizations of first-order logic is categorical. In addition, I argue that the open-endedness requirement does not make the first-order Peano Arithmetic categorical and I advance an argument for its categoricity based on the inferential conservativity requirement. (shrink)

Downsizing has become a significant public issue that has not yet been significantly studied by business ethicists. It is proposed that reasonable social and psychological contracts bound the moral free space of managers contemplating downsizing; the degree of constraint is also dependent on the organization's resource munificence. A framework for considering the extent of managerial moral free space and implications thereof for managerial practice are offered.

We investigate effective categoricity for polymodal algebras. We prove that the class of polymodal algebras is complete with respect to degree spectra of nontrivial structures, effective dimensions, expansion by constants, and degree spectra of relations. In particular, this implies that every categoricity spectrum is the categoricity spectrum of a polymodal algebra.

Defining the degree of categoricity of a computable structure ${\mathcal{M}}$ to be the least degree d for which ${\mathcal{M}}$ is d-computably categorical, we investigate which Turing degrees can be realized as degrees of categoricity. We show that for all n, degrees d.c.e. in and above 0 (n) can be so realized, as can the degree 0 (ω).

This article examines the traditional and modern doctrines of categorical propositions and argues that both doctrines have serious problems. While the doctrines disagree about existential imports...

Categorical Monism (that is, the view that all fundamental natural properties are purely categorical) has recently been challenged by a number of philosophers. In this paper, I examine a challenge which can be based on Gabriele Contessa’s [10] defence of the view that only powers can confer dispositions. In his paper Contessa argues against what he calls the Nomic Theory of Disposition Conferral (NTDC). According to NTDC, in each world in which they exist, (categorical) properties confer specific (...) dispositions on their bearers; yet, which disposition a (categorical) property confers on its bearers depends on what the (contingent) laws of nature happen to be. Contessa, inter alia, rests his case on an intuitive analogy between cases of mimicking (in which objects do not actually possess the dispositions associated with their displayed behaviour) and cases of disposition conferral through the action of laws. In this paper, I criticize various aspects of Contessa’s argumentation and show that the conclusion he arrives at (that is, only powers can confer dispositions) is controversial. (shrink)

The categorical dualities presented are: (first) for the category of bi-algebraic lattices that belong to the variety generated by the smallest non-modular lattice with complete (0,1)-lattice homomorphisms as morphisms, and (second) for the category of non-trivial (0,1)-lattices belonging to the same variety with (0,1)-lattice homomorphisms as morphisms. Although the two categories coincide on their finite objects, the presented dualities essentially differ mostly but not only by the fact that the duality for the second category uses topology. Using the presented (...) dualities and some known in the literature results we prove that the Q-lattice of any non-trivial variety of (0,1)-lattices is either a 2-element chain or is uncountable and non-distributive. (shrink)

We argue that the basic notions of mathematics can only be properly formulated in an informal way. Mathematical notions transcend formalizations and their study involves the consideration of other mathematical notions. We explain the fundamental role of categoricity theorems in making these studies possible. We arrive at the conclusion that the enterprise of mathematics is not infallible and that it ultimately relies on degrees of evidence.

This paper defends the doctrine that moral requirements are categorical in nature. My point of departure is John McDowell’s 1978 essay, “Are Moral Requirements Hypothetical Imperatives?”, in which McDowell argues, against Philippa Foot, that moral reasons are not conditional upon agents’ desires and are, in a certain sense, inescapable. After expounding McDowell’s view, exploring his idea that moral requirements “silence” other considerations and discussing its particularist ethos, I address an objection that moral reasons, as McDowell conceives them, are fundamentally (...) incomplete in ways only a full-bloodedly Kantian appeal to pure practical reason can remedy. I conclude that the objection fails: ordinary moral reasons do not stand in need of a grounding in Reason. There is no prospect of deriving them from a supreme principle of morality or other canons of rationality. Ordinary reasons are sufficient in themselves, though their significance can be elucidated and illuminated by various strategies — some broadly Aristotelian, some drawing inspiration from Kant’s formula of humanity — in ways that can strengthen and vindicate them. Notwithstanding the failure of the objection, I conclude by reflecting on how Kantian insights can yet play a significant role in a McDowellian view of moral deliberation and moral education. (shrink)

This paper largely engages with Brian Ellis’s description of categorical dimensions as put forward in his paper in this volume. The New Essentialism advocated by Ellis posits the ontologically-robust existence of both dispositional and categorical properties. I have argued that the distinction that Ellis draws between the two is unpersuasive, and that the causal role of categorical dimensions—what they do—is inseparable from what they are. This observation is reinforced by the fact that absolute physical quantities permit re-interpretations (...) of measurement that remove a clear differentiation between categoricity and dispositionality. Distinguishing between ‘pure power’ and ‘dispositionality’, I further argue that: i) there are no ontologically-robust categorical properties, although their apparent existence is explicable as higher-order and supervenient; ii) that the fundamental ingredients of the world may be accounted for in terms of pure-power that is neither categorical nor dispositional; and iii) that the categorical-dispositional distinction arises only at the higher-order level of objects, and does not in any case constitute ontologically-robust partitioning of reality. -/- . (shrink)

Discussions about dispositional and categorical properties have become commonplace in metaphysics. Unfortunately, dispositionality and categoricity are disputed notions: usual characterizations are piecemeal and not widely applicable, thus threatening to make agreements and disagreements on the matter merely verbal—and also making it arduous to map a logical space of positions about dispositional and categorical properties in which all parties can comfortably fit. This paper offers a prescription for this important difficulty, or at least an inkling thereof. This will be (...) achieved by comparing pairs of positions and exploring their background metaphysics to discover where alleged agreements and disagreements concerning dispositionality and categoricity really lie; more specifically, the Pure Powers view and the Powerful Qualities view will be under scrutiny. Over this background, the prescription functions by isolating a successful identity-based characterization of categoricity, while abandoning the correspondent identity-based characterization of dispositionality. On the contrary, according to this prescription a property is dispositional if and only if it is solely in virtue of possessing that property that its bearer is assigned a certain dispositional profile. A crucial consequence of this prescription is that, while supporters of the Pure Powers view often characterize their position as an essentialist one, the dispositionality of properties needn’t always be a matter of essence. (shrink)

The third author has shown that Shelah's eventual categoricity conjecture holds in universal classes: class of structures closed under isomorphisms, substructures, and unions of chains. We extend this result to the framework of multiuniversal classes. Roughly speaking, these are classes with a closure operator that is essentially algebraic closure (instead of, in the universal case, being essentially definable closure). Along the way, we prove in particular that Galois (orbital) types in multiuniversal classes are determined by their finite restrictions, generalizing a (...) result of the second author. (shrink)

In this paper, we give a classification of ℵ0-categorical coloured linear orders, generalizing Rosenstein's characterization of ℵ0-categorical linear orderings. We show that they can all be built from coloured singletons by concatenation and ℚn-combinations . We give a method using coding trees to describe all structures in our list.

Kant has argued that moral requirements are categorical. Kant's claim has been challenged by some contemporary philosophers; this article defends Kant's doctrine. I argue that Kant's claim captures the unique feature of moral requirements. The main arguments against Kant's claim focus on one condition that a categorical imperative must meet: to be independent of desires. I argue that there is another important, but often ignored, condition that a categorical imperative must meet, and this second condition is crucial (...) to understanding why moral requirements are not hypothetical. I also argue that the claim that moral requirements are not categorical because they depend on desires for motivation is beside the point. The issue of whether moral requirements are categorical is not an issue about whether moral desires or feelings are necessary for moral motivation but are rather an issue about the ground of moral desires or moral feelings. Moral requirements are categorical because they are requirements of reason, and reason makes moral desires or feelings possible. (shrink)

We provide here the first steps toward a Classification Theory ofElementary Classes with no maximal models, plus some mild set theoretical assumptions, when the class is categorical in some λ greater than its Löwenheim-Skolem number. We study the degree to which amalgamation may be recovered, the behaviour of non μ-splitting types. Most importantly, the existence of saturated models in a strong enough sense is proved, as a first step toward a complete solution to the o Conjecture for these classes. (...) Further results are in preparation. (shrink)

This paper offers a conceptual clarification of the phenomenon commonly referred to as categorical perception of color, both in adults and in infants. First, I argue against the common notion of categorical perception as involving a distortion of the perceptual color space. The effects observed in the categorical perception research concern categorical discrimination performance and the underlying processing; they need not directly reflect the relations of color similarity and difference. Moreover, the methodology of the research actually (...) presupposes that the relations of similarity and difference do not vary with languages. The observed categorical perception effects should be conceived independently of the perceptual color space. Second, I challenge the usual opinion that the existing evidence on infant “categorical perception” allows us to conclude that infants perceptually categorize color, and in particular, that they have perceptual categories that resemble the basic color categories of English. Such conclusions rest on an unjustified interpretation of the infant “categorical perception” findings in terms of adult linguistic categorical boundaries. Based on the suggested new understanding, I propose that the phenomenon, as present in infants, should be conceived and examined as a possible explanatory factor with respect to the existing patterns of color naming in languages of the world. (shrink)

The dispute between Kantians and Humeans over whether practical reason can justify moral reasons for all agents is often characterized as a debate over whether reasons are hypothetical or categorical. Instead, this debate must be understood in terms of the distinction between agent-neutral and agent-relative reasons. This paper considers Alan Gewirth’s Reason and Morality as a case study of a Kantian justification of morality focused on deriving categorical reasons from hypothetical reasons. The case study demonstrates first, the possibility (...) of categorical agent-relative reasons, and second, that inattention to this possibility has caused considerable confusion in the debate between Kantians and Humeans. (shrink)

In his article 'Rejection' (1996), Timothy Smiley had shown how a logical system allowing rules of rejection could provide a categorical axiomatization of the classical propositional calculus. This paper shows how rules of rejection, when placed in a multiple conclusion setting, can also provide categorical axiomatizations of a range of non-classical calculi which permit truth-value gaps, among them the calculus in Smiley's own 'Sense without denotation' (1960).

Let be an abstract elementary class with amalgamation, and Lowenheim Skolem number LS. We prove that for a suitable Hanf number gc0 if χ0 < λ0 λ1, and is categorical inλ1+ then it is categorical in λ0.

One of the few points of consensus in the Kantian literature is that Kant’s Moral Law is binding universally and unconditionally. Hence, the Moral Law is binding for all human agents (universally) irrespective of the agents’ particular interests (unconditionally). Whether or not we intend to act on the Moral Law, this is the law we ought to follow. Beyond this point of consensus, however, even the most important details are matters of controversy. What exactly does the Moral Law require of (...) us? What, if anything, grounds its bindingness? In particular, does Kant argue that the Moral Law is binding because it is ‘self-legislated’? What is the relation between the Moral Law (supreme principle of morality) and substantive moral laws such as the law that we ought to promote the happiness of others? What does Kant mean by his claim that the will has autonomy? In the four articles discussed in this special issue, Kleingeld proposes novel answers to these questions. This introduction presents the articles and brings to the fore the larger theme tying them all together. (shrink)

We investigate effective categoricity of computable equivalence structures . We show that is computably categorical if and only if has only finitely many finite equivalence classes, or has only finitely many infinite classes, bounded character, and at most one finite k such that there are infinitely many classes of size k. We also prove that all computably categorical structures are relatively computably categorical, that is, have computably enumerable Scott families of existential formulas. Since all computable equivalence structures (...) are relatively categorical, we further investigate when they are categorical. We also obtain results on the index sets of computable equivalence structures. (shrink)

Summary We have considered complete consistent systems in the first‐oder predicate calculus with identity, and have studied the set of the models of such a system by means of the maximal consistent condition‐sets associated with the system. The results may be summarized thus: (a) A complete consistent system is no‐categorical (= categorical in the denumerable domain) if and only if for every n, the number of different conditions in n variables is finite (T10). (b) If a complete consistent (...) system has a model M with finite character (i.e. a model M such that every maximal consistent condition‐set satisfied in M has a finite basis), then this model M is uniquely characterized by the property that every other model is an arithmetic extension of M (T 5). (c) Every complete consistent system, which has only a denumerable number of different associated maximal consistent condition‐sets, has a model with finite character (T8). (shrink)

This paper is devoted to the proof of the following upward categoricity theorem: Let K be a tame abstract elementary class with amalgamation, arbitrarily large models, and countable Löwenheim-Skolem number. If K is categorical in ‮א‬₁ then K is categorical in every uncountable cardinal. More generally, we prove that if K is categorical in a successor cardinal λ⁺ then K is categorical everywhere above λ⁺.

Studies of categorical induction typically examine how belief in a premise (e.g., Falcons have an ulnar artery) projects on to a conclusion (e.g., Robins have an ulnar artery). We study induction in cases in which the premise is uncertain (e.g., There is an 80% chance that falcons have an ulnar artery). Jeffrey's rule is a normative model for updating beliefs in the face of uncertain evidence. In three studies we tested the descriptive validity of Jeffrey's rule and a related (...) probability theorem, the rule of total probability. Although these rules provided good approximations to mean judgments in some cases, the results from regression and correlation analyses suggest that participants focus on the parts of these rules that are associated with the highest overall probability. We relate our findings to rational models of judgment. (shrink)

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and (...) class='Hi'>categorical sensing (CS) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing semiotic freedom observed in biological and cognitive systems. (shrink)

Categories can affect our perception of the world, rendering between-category differences more salient than within-category ones. Across many studies, such categorical perception has been observed for the basic-level categories of one's native language. Other research points to categorical distinctions beyond the basic level, but it does not demonstrate CP for such distinctions. Here we provide such a demonstration. Specifically, we show CP in English speakers for the non-basic distinction between “warm” and “cool” colors, claimed to represent the earliest (...) stage of color lexicon evolution. Notably, the advantage for discriminating colors that straddle the warm–cool boundary was restricted to the right visual field—the same behavioral signature previously observed for basic-level categories. This pattern held in a replication experiment with increased power. Our findings show that categorical distinctions beyond the basic-level repertoire of one's native language are psychologically salient and may be spontaneously accessed during normal perceptual processing. (shrink)

A categorical ontology of space and time is presented for emergent biosystems, super-complex dynamics, evolution and human consciousness. Relational structures of organisms and the human mind are naturally represented in non-abelian categories and higher dimensional algebra. The ascent of man and other organisms through adaptation, evolution and social co-evolution is viewed in categorical terms as variable biogroupoid representations of evolving species. The unifying theme of local-to-global approaches to organismic development, evolution and human consciousness leads to novel patterns of (...) relations that emerge in super- and ultra- complex systems in terms of colimits of biogroupoids, and more generally, as compositions of local procedures to be defined in terms of locally Lie groupoids. Solutions to such local-to-global problems in highly complex systems with ‘broken symmetry’ may be found with the help of generalized van Kampen theorems in algebraic topology such as the Higher Homotopy van Kampen theorem (HHvKT). Primordial organism structures are predicted from the simplest metabolic-repair systems extended to self-replication through autocatalytic reactions. The intrinsic dynamic ‘asymmetry’ of genetic networks in organismic development and evolution is investigated in terms of categories of many-valued, Łukasiewicz–Moisil logic algebras and then compared with those obtained for (non-commutative) quantum logics. The claim is defended in this essay that human consciousness is unique and should be viewed as an ultra-complex, global process of processes. The emergence of consciousness and its existence seem dependent upon an extremely complex structural and functional unit with an asymmetric network topology and connectivities—the human brain—that developed through societal co-evolution, elaborate language/symbolic communication and ‘virtual’, higher dimensional, non-commutative processes involving separate space and time perceptions. Philosophical theories of the mind are approached from the theory of levels and ultra-complexity viewpoints which throw new light on previous representational hypotheses and proposed semantic models in cognitive science. Anticipatory systems and complex causality at the top levels of reality are also discussed in the context of the ontological theory of levels with its complex/entangled/intertwined ramifications in psychology, sociology and ecology. The presence of strange attractors in modern society dynamics gives rise to very serious concerns for the future of mankind and the continued persistence of a multi-stable biosphere. A paradigm shift towards non-commutative, or non-Abelian, theories of highly complex dynamics is suggested to unfold now in physics, mathematics, life and cognitive sciences, thus leading to the realizations of higher dimensional algebras in neurosciences and psychology, as well as in human genomics, bioinformatics and interactomics. (shrink)

We describe punctual categoricity in several natural classes, including binary relational structures and mono-unary functional structures. We prove that every punctually categorical structure in a finite unary language is${\text {PA}}(0')$-categorical, and we show that this upper bound is tight. We also construct an example of a punctually categorical structure whose degree of categoricity is$0''$. We also prove that, with a bit of work, the latter result can be pushed beyond$\Delta ^1_1$, thus showing that punctually categorical structures (...) can possess arbitrarily complex automorphism orbits.As a consequence, it follows that binary relational structures and unary structures are not universal with respect to primitive recursive interpretations; equivalently, in these classes every rich enough interpretation technique must necessarily involve unbounded existential quantification or infinite disjunction. In contrast, it is well-known that both classes are universal for Turing computability. (shrink)

We show that the categoricity of second-order Peano axioms can be proved from the comprehension axioms. We also show that the categoricity of second-order Zermelo–Fraenkel axioms, given the order type of the ordinals, can be proved from the comprehension axioms. Thus these well-known categoricity results do not need the so-called “full” second-order logic, the Henkin second-order logic is enough. We also address the question of “consistency” of these axiom systems in the second-order sense, that is, the question of existence of (...) models for these systems. In both cases we give a consistency proof, but naturally we have to assume more than the mere comprehension axioms. (shrink)

During public health crises including the COVID-19 pandemic, resource scarcity and contagion risks may require health systems to shift—to some degree—from a usual clinical ethic, focused on the well-being of individual patients, to a public health ethic, focused on population health. Many triage policies exist that fall under the legal protections afforded by “crisis standards of care,” but they have key differences. We critically appraise one of the most fundamental differences among policies, namely the use of criteria to categorically exclude (...) certain patients from eligibility for otherwise standard medical services. We examine these categorical exclusion criteria from ethical, legal, disability, and implementation perspectives. Focusing our analysis on the most common type of exclusion criteria, which are disease-specific, we conclude that optimal policies for critical care resource allocation and the use of cardiopulmonary resuscitation (CPR) should not use categorical exclusions. We argue that the avoidance of categorical exclusions is often practically feasible, consistent with public health norms, and mitigates discrimination against persons with disabilities. (shrink)

We prove that each ω-categorical, generically stable group is solvable-by-finite.

An explicit categorical equivalence is defined between a proper subvariety of the class of \-algebras, as defined by Di Nola and Dvurečenskij, to be called \-algebras, and the category of semi-low \-rings. This categorical representation is done using the prime spectrum of the \-algebras, through the equivalence between \-algebras and \-groups established by Mundici, from the perspective of the Dubuc–Poveda approach, that extends the construction defined by Chang on chains. As a particular case, semi-low \-rings associated to Boolean (...) algebras are characterized. (shrink)

We present in this paper an abstract categorical logic based on an abstraction of quantifier. More precisely, the proposed logic is abstract because no structural constraints are imposed on models (semantics free). By contrast, formulas are inductively defined from an abstraction both of atomic formulas and of quantifiers. In this sense, the proposed approach differs from other works interested in formalizing the notion of abstract logic and of which the closest to our approach are the institutions, which in addition (...) to be semantics free do not also impose any syntactic contingencies on the structure of formulas. To define the semantical framework in which formulas will be interpreted, we propose to follow the idea from categorical logic which defines the semantical interpretation of formulas from context and as subobjects of an object of a given category. In the spirit of Lawvere’s hyperdoctrines, we use a more abstract notion which generalizes the notion of subobject, standard in category theory: Pitt’s prop-categories. Always in the spirit of categorical logic, we propose a sequent calculus of which we show correctness and completeness for all semantical frameworks defined over any prop-categories. We then study some conditions which allow us to get this completeness result for particular classes of prop-categories. (shrink)

We explore the interplay between $\omega $ -categoricity and pseudofiniteness for groups, and we conjecture that $\omega $ -categorical pseudofinite groups are finite-by-abelian-by-finite. We show that the conjecture reduces to nilpotent p-groups of class 2, and give a proof that several of the known examples of $\omega $ -categorical p-groups satisfy the conjecture. In particular, we show by a direct counting argument that for any odd prime p the ( $\omega $ -categorical) model companion of the theory (...) of nilpotent class 2 exponent p groups, constructed by Saracino and Wood, is not pseudofinite, and that an $\omega $ -categorical group constructed by Baudisch with supersimple rank 1 theory is not pseudofinite. We also survey some scattered literature on $\omega $ -categorical groups over 50 years. (shrink)

Hellman [2003] raises interesting challenges to categorical structuralism. He starts citing Awodey [1996] which, as Hellman sees, is not intended as a foundation for mathematics. It offers a structuralist framework which could denned in any of many different foundations. But Hellman says Awodey's work is 'naturally viewed in the context of Mac Lane's repeated claim that category theory provides an autonomous foundation for mathematics as an alternative to set theory' (p. 129). Most of Hellman's paper 'scrutinizes the formulation of (...) category theory' specifically in 'its alleged role as providing a foundation' (p. 130). I will also focus on the foundational question. Page numbers in parentheses are page references to Hellman [2003]. (shrink)

We explore approximate categoricity in the context of distortion systems, introduced in our previous paper (Hanson in Math Logic Q 69(4):482–507, 2023), which are a mild generalization of perturbation systems, introduced by Yaacov (J Math Logic 08(02):225–249, 2008). We extend Ben Yaacov’s Ryll-Nardzewski style characterization of separably approximately categorical theories from the context of perturbation systems to that of distortion systems. We also make progress towards an analog of Morley’s theorem for inseparable approximate categoricity, showing that if there is (...) some uncountable cardinal $$\kappa $$ such that every model of size $$\kappa $$ is ‘approximately saturated,’ in the appropriate sense, then the same is true for all uncountable cardinalities. Finally we present some examples of these phenomena and highlight an apparent interaction between ordinary separable categoricity and inseparable approximate categoricity. (shrink)

On a widespread naturalist view, the meanings of mathematical terms are determined, and can only be determined, by the way we use mathematical language—in particular, by the basic mathematical principles we’re disposed to accept. But it’s mysterious how this can be so, since, as is well known, minimally strong first-order theories are non-categorical and so are compatible with countless non-isomorphic interpretations. As for second-order theories: though they typically enjoy categoricity results—for instance, Dedekind’s categoricity theorem for second-order and Zermelo’s quasi-categoricity (...) theorem for second-order —these results require full second-order logic. So appealing to these results seems only to push the problem back, since the principles of second-order logic are themselves non-categorical: those principles are compatible with restricted interpretations of the second-order quantifiers on which Dedekind’s and Zermelo’s results are no longer available. In this paper, we provide a naturalist-friendly, non-revisionary solution to an analogous but seemingly more basic problem—Carnap’s Categoricity Problem for propositional and first-order logic—and show that our solution generalizes, giving us full second-order logic and thereby securing the categoricity or quasi-categoricity of second-order mathematical theories. Briefly, the first-order quantifiers have their intended interpretation, we claim, because we’re disposed to follow the quantifier rules in an open-ended way. As we show, given this open-endedness, the interpretation of the quantifiers must be permutation-invariant and so, by a theorem recently proved by Bonnay and Westerståhl, must be the standard interpretation. Analogously for the second-order case: we prove, by generalizing Bonnay and Westerståhl’s theorem, that the permutation invariance of the interpretation of the second-order quantifiers, guaranteed once again by the open-endedness of our inferential dispositions, suffices to yield full second-order logic. (shrink)

For a computable structure $\mathcal {M}$, the categoricity spectrum is the set of all Turing degrees capable of computing isomorphisms among arbitrary computable copies of $\mathcal {M}$. If the spectrum has a least degree, this degree is called the degree of categoricity of $\mathcal {M}$. In this paper we investigate spectra of categoricity for computable rigid structures. In particular, we give examples of rigid structures without degrees of categoricity.

An important part of the theory of algebraizable sentential logics consists of studying the algebraic semantics of these logics. As developed by Czelakowski, Blok, and Pigozzi and Font and Jansana, among others, it includes studying the properties of logical matrices serving as models of deductive systems and the properties of abstract logics serving as models of sentential logics. The present paper contributes to the development of the categorical theory by abstracting some of these model theoretic aspects and results from (...) the level of sentential logics to the level of π-institutions. (shrink)

In proof-theoretic semantics, model-theoretic validity is replaced by proof-theoretic validity. Validity of formulae is defined inductively from a base giving the validity of atoms using inductive clauses derived from proof-theoretic rules. A key aim is to show completeness of the proof rules without any requirement for formal models. Establishing this for propositional intuitionistic logic raises some technical and conceptual issues. We relate Sandqvist’s (complete) base-extension semantics of intuitionistic propositional logic to categorical proof theory in presheaves, reconstructing categorically the soundness (...) and completeness arguments, thereby demonstrating the naturality of Sandqvist’s constructions. This naturality includes Sandqvist’s treatment of disjunction that is based on its second-order or elimination-rule presentation. These constructions embody not just validity, but certain forms of objects of justifications. This analysis is taken a step further by showing that from the perspective of validity, Sandqvist’s semantics can also be viewed as the natural disjunction in a category of sheaves. (shrink)