Model transfer refers to the observation that particular model structures are used across multiple distinct scientific domains. This paper puts forward an account to explain the inter-domain transfer of model structures. Central in the account is the role of validation criteria in determining whether a model is considered to be useful by practitioners. Validation criteria are points of reference to which model correctness for a particular purpose is assessed. I argue that validation criteria can be categorized as being mathematical, theoretical (...) or phenomenological in nature. Model transfer is explained by overlap in validation criteria between scientific domains. Particular emphasis is placed on overlap between phenomenological criteria. Overlap in phenomenological criteria can be explained through the notion of universal patterns. Universal patterns are abstract structures that can be made to refer to multiple distinct phenomena when coupled with phenomena-specific empirical content. I present the case study of the Yule Process, in which universal patterns play a crucial role in explaining model transfer. This paper provides an account of model transfer that stays close to modelling practice and expands existing accounts by introducing the notion of universal patterns. (shrink)

We study the connection between factors of the Medvedev lattice and constructive logic. The algebraic properties of these factors determine logics lying in between intuitionistic propositional logic and the logic of the weak law of the excluded middle (also known as De Morgan, or Jankov, logic). We discuss the relation between the weak law of the excluded middle and the algebraic notion of join-reducibility. Finally we discuss autoreducible degrees.

This book is the first part of a comprehensive study of Wittgenstein's conception of language description. Describing language was no pastime occupation for the philosopher. It was hard work and it meant struggle. It made for a philosophy that required Wittgenstein's full attention and half his life. His approach had always been working on himself, on how he saw things. The central claim of this book is that nothing will come of our exegetical efforts to see what Wittgenstein's later philosophy (...) amounts to if his work on describing language is not given the place and concern it deserves. The book shows what his philosophy might begin to look like in the light of critical questions around his interest to see the end of the day with descriptions, and these things only. (shrink)

We investigate the structure of the Medvedev lattice as a partial order. We prove that every interval in the lattice is either finite, in which case it is isomorphic to a finite Boolean algebra, or contains an antichain of size $2^{2^{\aleph }0}$ , the size of the lattice itself. We also prove that it is consistent with ZFC that the lattice has chains of size $2^{2^{\aleph }0}$ , and in fact these big chains occur in every infinite interval. We also (...) study embeddings of lattices and algebras. We show that large Boolean algebras can be embedded into the Medvedev lattice as upper semilattices, but that a Boolean algebra can be embedded as a lattice only if it is countable. Finally we discuss which of these results hold for the closely related Muchnik lattice. (shrink)

ABSTRACT In the work of Ernesto Laclau, populism is treated as a hegemonic challenge. Hegemony describes the usurpation of the image of society as a totality by a particular and underdetermined social imaginary. Seen through the lens of what Johann P. Arnason terms “post-transcendental phenomenology”, this concerns the way in which a society sees and experiences both itself and the world it inhabits. This article suggests that hegemonic social imaginaries are built into a society’s public spaces, and are in turn (...) experienced by citizens moving through these spaces, meaning that the built environment is central to the development of populist imaginaries. The article discusses how the neoliberal city exemplifies the way social imaginaries are inscribed into the physical landscape by highlighting three moments in the city; the institution of a certain imaginary as dominant; its sedimentation within the urban fabric over time; and finally, the re-activation of the original moment of institution, which opens up the possibility for new beginnings to overwrite the imaginaries encoded in the city. These three moments describe how physical, built spaces make concrete the power relations and horizons of possibility of the hegemonic imaginary—making possible and encouraging certain ways of being while discouraging (and hiding) others. This hegemonic logic of occupying a public space in the name of a particular subset of the population is a not only parallel to the form of populist politics, but populist sentiment is—at least in part—provoked by the experiences of inhabiting these spaces. (shrink)

We prove that there are uncountably many sets that are low for the class of Schnorr random reals. We give a purely recursion theoretic characterization of these sets and show that they all have Turing degree incomparable to 0'. This contrasts with a result of Kučera and Terwijn [5] on sets that are low for the class of Martin-Löf random reals.

In this study, we examine the influence of senior leadership on firms’ corporate social responsibility. We integrate upper echelons research that has investigated either the influence of the CEO or the top management team on CSR. We contend that functional experience complementarity between CEOs and TMTs in formulating and implementing CSR strategy may underlie differentiated strategies in CSR. We find that when CEOs who have predominant experience in output functions are complemented by TMTs with a lower proportion of members who (...) have experience in output functions, there is a pronounced effect on the community, product, and diversity dimensions of CSR. In turn, when output-oriented CEOs are complemented by output-oriented TMTs, we observe an effect on the employee relations dimension of CSR. Interestingly, we find no influence of CEO-TMT complementarity on the environment dimension of CSR. In general, our empirical results support the relevance of the interaction between CEOs and their TMTs in defining their firms’ CSR profile. (shrink)

Name der Zeitschrift: Wittgenstein-Studien Jahrgang: 5 Heft: 1 Seiten: 57-88.

Simpson introduced the lattice of Π0 1 classes under Medvedev reducibility. Questions regarding completeness in are related to questions about measure and randomness. We present a solution to a question of Simpson about Medvedev degrees of Π0 1 classes of positive measure that was independently solved by Simpson and Slaman. We then proceed to discuss connections to constructive logic. In particular we show that the dual of does not allow an implication operator (i.e. that is not a Heyting algebra). We (...) also discuss properties of the class of PA-complete sets that are relevant in this context. (shrink)

In this study, we examine the influence of senior leadership on firms’ corporate social responsibility. We integrate upper echelons research that has investigated either the influence of the CEO or the top management team on CSR. We contend that functional experience complementarity between CEOs and TMTs in formulating and implementing CSR strategy may underlie differentiated strategies in CSR. We find that when CEOs who have predominant experience in output functions are complemented by TMTs with a lower proportion of members who (...) have experience in output functions, there is a pronounced effect on the community, product, and diversity dimensions of CSR. In turn, when output-oriented CEOs are complemented by output-oriented TMTs, we observe an effect on the employee relations dimension of CSR. Interestingly, we find no influence of CEO-TMT complementarity on the environment dimension of CSR. In general, our empirical results support the relevance of the interaction between CEOs and their TMTs in defining their firms’ CSR profile. (shrink)

In the context of his theory of numberings, Ershov showed that Kleene's recursion theorem holds for any precomplete numbering. We discuss various generalizations of this result. Among other things, we show that Arslanov's completeness criterion also holds for every precomplete numbering, and we discuss the relation with Visser's ADN theorem, as well as the uniformity or nonuniformity of the various fixed point theorems. Finally, we base numberings on partial combinatory algebras and prove a generalization of Ershov's theorem in this context.

For every partial combinatory algebra, we define a hierarchy of extensionality relations using ordinals. We investigate the closure ordinals of pca’s, i.e., the smallest ordinals where these relations become equal. We show that the closure ordinal of Kleene’s first model is ${\omega _1^{\textit {CK}}}$ and that the closure ordinal of Kleene’s second model is $\omega _1$. We calculate the exact complexities of the extensionality relations in Kleene’s first model, showing that they exhaust the hyperarithmetical hierarchy. We also discuss embeddings of (...) pca’s. (shrink)

This book reconstructs and interprets the theory of the emotions as expounded by the Stoic philosopher Chrysippus in his 'On Affections', only fragments of which remain. Given its contextual approach, sources such as Galen and Cicero receive ample attention.

We define a variant of the standard Kripke semantics for intuitionistic logic, motivated by the connection between constructive logic and the Medvedev lattice. We show that while the new semantics is still complete, it gives a simple and direct correspondence between Kripke models and algebraic structures such as factors of the Medvedev lattice.

We investigate the initial segments of the Medvedev lattice as Brouwer algebras, and study the propositional logics connected to them.

A positive answer to a question of M. van Lambalgen and D. Zambella whether there exist nonrecursive sets that are low for the class of random sets is obtained. Here a set A is low for the class RAND of random sets if RAND = RAND A.

We develop arithmetical measure theory along the lines of Lutz [10]. This yields the same notion of measure 0 set as considered before by Martin-Löf, Schnorr, and others. We prove that the class of sets constructible by r.e.-constructors, a direct analogue of the classes Lutz devised his resource bounded measures for in [10], is not equal to RE, the class of r.e. sets, and we locate this class exactly in terms of the common recursion-theoretic reducibilities below K. We note that (...) the class of sets that bounded truth-table reduce to K has r.e.-measure 0, and show that this cannot be improved to truth-table. For Δ2-measure the borderline between measure zero and measure nonzero lies between weak truth-table reducibility and Turing reducibility to K. It follows that there exists a Martin-Löf random set that is tt-reducible to K, and that no such set is btt-reducible to K. In fact, by a result of Kautz, a much more general result holds. (shrink)

We prove a number of elementary facts about computability in partial combinatory algebras. We disprove a suggestion made by Kreisel about using Friedberg numberings to construct extensional pca’s. We then discuss separability and elements without total extensions. We relate this to Ershov’s notion of precompleteness, and we show that precomplete numberings are not 1–1 in general.

We discuss the effectivity of Arslanov’s completeness criterion. In particular, we show that a parameterized version, similar to the recursion theorem with parameters, fails. We also discuss the effectivity of another extension of the recursion theorem, namely Visser’s ADN theorem, as well as that of a joint generalization of the ADN theorem and Arslanov’s completeness criterion.

Partial combinatory algebras (pcas) are algebraic structures that serve as generalized models of computation. In this article, we study embeddings of pcas. In particular, we systematize the embeddings between relativizations of Kleene’s models, of van Oosten’s sequential computation model, and of Scott’s graph model, showing that an embedding between two relativized models exists if and only if there exists a particular reduction between the oracles. We obtain a similar result for the lambda calculus, showing in particular that it cannot be (...) embedded in Kleene’s first model. (shrink)

In this work, new light is thrown on the philosophical method of the great Stoic Chrysippus on the basis of the fragments preserved by Galen in his De Placitis books II-III. Included is a study of Galen's aims and methodologies.

We study the model-theoretic aspects of a probability logic suited for talking about measure spaces. This nonclassical logic has a model theory rather different from that of classical predicate logic. In general, not every satisfiable set of sentences has a countable model, but we show that one can always build a model on the unit interval. Also, the probability logic under consideration is not compact. However, using ultraproducts we can prove a compactness theorem for a certain class of weak models.

In " Enn." IV, 3. 23 Plotinus presents a vindication of the well - known tripartition - cum - trilocation of the soul advanced by Plato in the " Timaeus." His version of the Platonic doctrine is marked by a strong spatial separation between the three parts of the soul -- reason in the brain, will in the heart and desire in the liver. This article addresses two related questions : Can this position be squared with the Plotinian key doctrine (...) that the soul is incorporeal and indivisible? What are the nature and provenance of this particular version of the tripartition, which, in this form, is not warranted by the Platonic text? Plotinus enlists the support of the anatomical researches presented by Galen in his " On the doctrines of Hippocrates and Plato." At the same time he adapts the latter ' s demonstration in such a way as to safeguard the unity and incorporeality of the soul. The parts of the soul are not " in " the three main bodily organs in an ordinary sense -- only their activity takes place there. Plotinus arrives at this position through a clarification of the concept of archê as employed by Galen. His understanding of the soul ' s localisation is heavily indebted to Alexander ' s " On the soul ". Meanwhile he dissociates himself from the hylomorphism typical of both Alexander and Galen. Other features of his argument are explicable as motivated by the wish to emasculate the arguments used by Alexander in favour of the cardiocentric theory. The upshot is a sophisticated and improved defence of the Platonic tripartition which not only is scientifically up - to - date but coheres with some of Plotinus ' most deeply held metaphysical convictions. (shrink)

We study a class of formulas generalizing the weak law of the excluded middle and provide a characterization of these formulas in terms of Kripke frames and Brouwer algebras. We use these formulas to separate logics corresponding to factors of the Medvedev lattice.

Can the straight line be analysed mathematically such that it does not fall apart into a set of discrete points, as is usually done but through which its fundamental continuity is lost? And are there objects of pure mathematics that can change through time? Mathematician and philosopher L.E.J. Brouwer argued that the two questions are closely related and that the answer to both is "yes''. To this end he introduced a new kind of object into mathematics, the choice sequence. But (...) other mathematicians and philosophers have been voicing objections to choice sequences from the start. This book aims to provide a sound philosophical basis for Brouwer's choice sequences by subjecting them to a phenomenological critique in the style of the later Husserl. (shrink)

Teun Tieleman surveys the history of the philosophical notion of the ‘art of life’, starting from its originator Socrates and his ancient successors down to its role among present-day philosophers. Apart from Socrates, special attention is given to the Stoics, Nietzsche and Foucault. The way in which the notion was defined and functioned throughout the history of philosophy reveals an exceptionally fruitful interplay between continuity and originality.

In this work, new light is thrown on the philosophical method of the great Stoic Chrysippus on the basis of the fragments preserved by Galen in his _De Placitis_ books II-III. Included is a study of Galen's aims and methodologies.

This article is concerned with the often neglected physical side of Stoic anthropology. The care for one’s soul is central to the Stoic notion of the art of living. Yet a special status is reserved for the human body—in spite of its being subsumed under the class of ‘indifferents’. This status is explicable by reference to the fact that they regard the soul as a subtle kind of breath and hence as corporeal. As such, it is blended with the human (...) body through and through. Care for the soul therefore involves care for the body. Furthermore, the Stoic view of the human organism entails a special interest in physiognomy. These interrelated aspects are studied against the backdrop of the relevant medical theories used by the Stoics. (shrink)

We report on some recent work centered on attempts to understand when one set is more random than another. We look at various methods of calibration by initial segment complexity, such as those introduced by Solovay [125], Downey, Hirschfeldt, and Nies [39], Downey, Hirschfeldt, and LaForte [36], and Downey [31]; as well as other methods such as lowness notions of Kučera and Terwijn [71], Terwijn and Zambella [133], Nies [101, 100], and Downey, Griffiths, and Reid [34]; higher level randomness notions (...) going back to the work of Kurtz [73], Kautz [61], and Solovay [125]; and other calibrations of randomness based on definitions along the lines of Schnorr [117].These notions have complex interrelationships, and connections to classical notions from computability theory such as relative computability and enumerability. Computability figures in obvious ways in definitions of effective randomness, but there are also applications of notions related to randomness in computability theory. For instance, an exciting by-product of the program we describe is a more-or-less naturalrequirement-freesolution to Post's Problem, much along the lines of the Dekker deficiency set. (shrink)

This article was derived from my doctoral thesis, ‘Post-apartheid racism among Afrikaans speaking urban adolescents: A narrative-pastoral reflection’. The impetus for this study was the seemingly increasing occurrences of racism amongst post-apartheid Afrikaans-speaking urban adolescents in South Africa by taking a narrative practical theological perspective on the matter to help build meaningful cross-cultural dialogue. This study explored the level of dialogue of the participants using a postfoundational paradigm. Two questions guided the investigation: How deeply embedded are objectifying of cross-cultural relationships? (...) How can we instigate honest dialogue aiding us in being more aware of our biases to embrace diversity and going forward as a unity in diversity? This study was conducted in 2016 amongst white Afrikaans-speaking urban adolescents living in Pretoria-East, South Africa. I had four group conversations with my co-researchers, with six to eight adolescents per group. I made use of certain empirical research methods, such as narrative interviewing and group discussions. From an epistemological perspective, a postfoundational, social constructionist perspective, including an auto-ethnographical approach, was followed. The research indicated that Afrikaner adolescents could live life unquestioned from a position of power and objectivity that was culturally inherited. It was found that by objectifying relationships, diverse engagement becomes almost impossible. Consequently, this article advocates for a dialogical approach towards building relationships in a context where people feel vulnerable and shameful, have fears, but also gain trust to contribute to meaningful dialogue with ‘others’. (shrink)

We compare various notions of algorithmic randomness. First we consider relativized randomness. A set is n-random if it is Martin-Löf random relative to ∅. We show that a set is 2-random if and only if there is a constant c such that infinitely many initial segments x of the set are c-incompressible: C ≥ |x|-c. The ‘only if' direction was obtained independently by Joseph Miller. This characterization can be extended to the case of time-bounded C-complexity. Next we prove some results (...) on lowness. Among other things, we characterize the 2-random sets as those 1-random sets that are low for Chaitin's Ω. Also, 2-random sets form minimal pairs with 2-generic sets. The r.e. low for Ω sets coincide with the r.e. K-trivial ones. Finally we show that the notions of Martin-Löf randomness, recursive randomness, and Schnorr randomness can be separated in every high degree while the same notions coincide in every non-high degree. We make some remarks about hyperimmune-free and PA-complete degrees. (shrink)