We introduce constructive and classical systems for nonstandard arithmetic and show how variants of the functional interpretations due to Gödel and Shoenfield can be used to rewrite proofs performed in these systems into standard ones. These functional interpretations show in particular that our nonstandard systems are conservative extensions of E-HAω and E-PAω, strengthening earlier results by Moerdijk and Palmgren, and Avigad and Helzner. We will also indicate how our rewriting algorithm can be used for term extraction purposes. To conclude the (...) paper, we will point out some open problems and directions for future research, including some initial results on saturation principles. (shrink)

This is the first in a series of papers on Predicative Algebraic Set Theory, where we lay the necessary groundwork for the subsequent parts, one on realizability [B. van den Berg, I. Moerdijk, Aspects of predicative algebraic set theory II: Realizability, Theoret. Comput. Sci. . Available from: arXiv:0801.2305, 2008], and the other on sheaves [B. van den Berg, I. Moerdijk, Aspects of predicative algebraic set theory III: Sheaf models, 2008 ]. We introduce the notion of a predicative category (...) with small maps and show that it provides a sound and complete semantics for constructive set theories like IZF and CZF. The main technical contribution of this paper is that it shows in detail that such categories can always be conservatively embedded in categories that are exact. These exactness properties play a crucial rôle in showing that predicative categories with small maps contain models of set theory and that they are closed under sheaves and realizability. We will prove the former statement in this paper as well, leaving a proof of the closure properties to the papers on realizability and sheaves as mentioned above. (shrink)

Kant’s views on animals have received much attention in recent years. According to some, Kant attributed the capacity for objective perceptual awareness to non-human animals, even though he denied that they have concepts. This position is difficult to square with a conceptualist reading of Kant, according to which objective perceptual awareness requires concepts. Others take Kant’s views on animals to imply that the mental life of animals is a blooming, buzzing confusion. In this article I provide a historical reconstruction of (...) Kant’s views on animals, relating them to eighteenth-century debates on animal cognition. I reconstruct the views of Buffon and Reimarus and show that (i) both Buffon and Reimarus adopted a conceptualist position, according to which concepts structure the cognitive experience of adult humans, and (ii) that both described the mental life of animals as a blooming, buzzing confusion. Kant’s position, I argue, is virtually identical to that of Reimarus. Hence Kant’s views on animals support a conceptualist reading of Kant. The article further articulates the historical antecedents of the Kantian idea that concepts structure human cognitive experience and provides a novel account of how the ideas of similarity and difference were conceptualized in eighteenth-century debates on animal cognition. (shrink)

In the present paper I investigate the role that analogy plays in eighteenth-century biology and in Kant’s philosophy of biology. I will argue that according to Kant, biology, as it was practiced in the eighteenth century, is fundamentally based on analogical reflection. However, precisely because biology is based on analogical reflection, biology cannot be a proper science. I provide two arguments for this interpretation. First, I argue that although analogical reflection is, according to Kant, necessary to comprehend the nature of (...) organisms, it is also necessarily insufficient to fully comprehend the nature of organisms. The upshot of this argument is that for Kant our understanding of organisms is necessarily limited. Second, I argue that Kant did not take biology to be a proper science because biology was based on analogical arguments. I show that Kant stemmed from a philosophical tradition that did not assign analogical arguments an important justificatory role in natural science. Analogy, according to this conception, does not provide us with apodictically certain cognition. Hence, sciences based on analogical arguments cannot constitute proper sciences. (shrink)

Ernst Mayr argued that the emergence of biology as a special science in the early nineteenth century was possible due to the demise of the mathematical model of science and its insistence on demonstrative knowledge. More recently, John Zammito has claimed that the rise of biology as a special science was due to a distinctive experimental, anti-metaphysical, anti-mathematical, and anti-rationalist strand of thought coming from outside of Germany. In this paper we argue that this narrative neglects the important role played (...) by the mathematical and axiomatic model of science in the emergence of biology as a special science. We show that several major actors involved in the emergence of biology as a science in Germany were working with an axiomatic conception of science that goes back at least to Aristotle and was popular in mid-eighteenth-century German academic circles due to its endorsement by Christian Wolff. More specifically, we show that at least two major contributors to the emergence of biology in Germany—Caspar Friedrich Wolff and Gottfried Reinhold Treviranus—sought to provide a conception of the new science of life that satisfies the criteria of a traditional axiomatic ideal of science. Both C.F. Wolff and Treviranus took over strong commitments to the axiomatic model of science from major philosophers of their time, Christian Wolff and Friedrich Wilhelm Joseph Schelling, respectively. The ideal of biology as an axiomatic science with specific biological fundamental concepts and principles thus played a role in the emergence of biology as a special science. (shrink)

Van den Berg, I.P., Extended use of IST, Annals of Pure and Applied Logic 58 73–92. Internal Set Theory is an axiomatic approach to nonstandard analysis, consisting of three axiom schemes, Transfer , Idealization , and Standardization . We show that the range of application of these axiom schemes may be enlarged with respect to the original formulation. Not only more kinds of formulas are allowed, but also different settings. Many examples illustrate these extensions. Most concern formal aspects of (...) nonstandard asymptotics. (shrink)

This book explores the various views on language and its relation to philosophy in the Platonic tradition by examening the reception of Plato's Cratylus in antiquity in general, and the commentary of the Neoplatonist Proclus in particular.

Kant is well known for his restrictive conception of proper science. In the present paper I will try to explain why Kant adopted this conception. I will identify three core conditions which Kant thinks a proper science must satisfy: systematicity, objective grounding, and apodictic certainty. These conditions conform to conditions codified in the Classical Model of Science. Kant’s infamous claim that any proper natural science must be mathematical should be understood on the basis of these conditions. In order to substantiate (...) this reading, I will show that only in this way it can be explained why Kant thought (1) that mathematics has a particular foundational function with respect to the natural sciences and (2) as such secures their scientific status. (shrink)

Biology in the Critical Philosophy and the Opus postumum Hein van den Berg. Parts of Chap. 2 have been previously published in Hein van den Berg (2011), “ Kant's Conception of Proper Science.” Synthese 183 (1): 7–26. Parts of Chap.

We study a new proof principle in the context of constructive Zermelo-Fraenkel set theory based on what we will call “non-deterministic inductive definitions”. We give applications to formal topology as well as a predicative justification of this principle.

This paper analyzes Immanuel Kant’s views on mechanical explanation on the basis of Christian Wolff’s idea of scientific demonstration. Kant takes mechanical explanations to explain properties of wholes in terms of their parts. I reconstruct the nature of such explanations by showing how part-whole conceptualizations in Wolff’s logic and metaphysics shape the ideal of a proper and explanatory scientific demonstration. This logico-philosophical background elucidates why Kant construes mechanical explanations as ideal explanations of nature.

Using the theory of exact completions, I construct a certain class of pretoposes, consisting of what one might call “predicative realizability toposes”, that can act as categorical models of certain predicative type theories, including Martin-Löf Type Theory.

We propose an extension of Aczel's constructive set theory CZF by an axiom for inductive types and a choice principle, and show that this extension has the following properties: it is interpretable in Martin-Löf's type theory. In addition, it is strong enough to prove the Set Compactness theorem and the results in formal topology which make use of this theorem. Moreover, it is stable under the standard constructions from algebraic set theory, namely exact completion, realizability models, forcing as well as (...) more general sheaf extensions. As a result, methods from our earlier work can be applied to show that this extension satisfies various derived rules, such as a derived compactness rule for Cantor space and a derived continuity rule for Baire space. Finally, we show that this extension is robust in the sense that it is also reflected by the model constructions from algebraic set theory just mentioned. (shrink)

This paper studies Sentence 16 of Porphyry’s Pathways to the Intelligible. It is argued that it should be understood against the background of Plotinus’ discussions of the similes of the waxen block and the aviary from Plato’s Theaetetus. The first part of the paper concentrates on Plotinus’ reception of these similes. In the second part of the paper Plotinus’ discussions of the two similes are used to shed light on Sentence 16, in particular on the term προχείρισις. Furthermore it is (...) argued that Porphyry does not reject Plotinus’ claim that, pace Aristotle, intellection does not require imaging. (shrink)

Non-well-founded trees are used in mathematics and computer science, for modelling non-well-founded sets, as well as non-terminating processes or infinite data structures. Categorically, they arise as final coalgebras for polynomial endofunctors, which we call M-types. We derive existence results for M-types in locally cartesian closed pretoposes with a natural numbers object, using their internal logic. These are then used to prove stability of such categories with M-types under various topos-theoretic constructions; namely, slicing, formation of coalgebras , and sheaves for an (...) internal site. (shrink)

Kant’s teleology as presented in the Critique of Judgment is commonly interpreted in relation to the late eighteenth-century biological research of Johann Friedrich Blumenbach. In the present paper, I show that this interpretative perspective is incomplete. Understanding Kant’s views on teleology and biology requires a consideration of the teleological and biological views of Christian Wolff and his rationalist successors. By reconstructing the Wolffian roots of Kant’s teleology, I identify several little known sources of Kant’s views on biology. I argue that (...) one of Kant’s main contributions to eighteenth-century debates on biology consisted in demarcating biology from metaphysics. Kant rejected Wolffian views on the hierarchy of sciences, according to which propositions specifying the functions of organisms are derived from theological truths. In addition, Kant argued that organic self-organization necessitates a teleological description in order to show that self-organization does not support materialism. By demarcating biology and metaphysics, Kant made a small yet important contribution to establishing biology as a science. (shrink)

The paper uses the formalism of indexed categories to recover the proof of a standard final coalgebra theorem, thus showing existence of final coalgebras for a special class of functors on finitely complete and cocomplete categories. As an instance of this result, we build the final coalgebra for the powerclass functor, in the context of a Heyting pretopos with a class of small maps. This is then proved to provide models for various non-well-founded set theories, depending on the chosen axiomatisation (...) for the class of small maps. (shrink)

The nonstandard stroboscopy method links discrete-time ordinary difference equations of first-order and continuous-time, ordinary differential equations of first order. We extend this method to the second order, and also to an elementary, yet general class of partial difference/differential equations, both of first and second order. We thus obtain straightforward discretizations and continuizations, even avoiding change of variables. In fact, we create intermediary objects: partial difference equations with S-continuous solutions, which have both discrete and continuous properties.

In this paper we investigate Accardi's claim that the "quantum paradoxes" have their roots in probability theory and that, in particular, they can be evaded by giving up Bayes' rule, concerning the relation between composite and conditional probabilities. We reach the conclusion that, although it may be possible to give up Bayes' rule and define conditional probabilities differently, this contributes nothing to solving the philosophical problems which surround quantum mechanics.

The History of Ideas is presently enjoying a certain renaissance after a long period of disrepute. Increasing quantities of digitally available historical texts and the availability of computational tools for the exploration of such masses of sources, it is suggested, can be of invaluable help to historians of ideas. The question is: how exactly? In this paper, we argue that a computational history of ideas is possible if the following two conditions are satisfied: (i) Sound Method . A computational history (...) of ideas must be built upon a sound theoretical foundation for its methodology, and the only such foundation is given by the use of models , i.e., fully explicit and revisable interpretive frameworks or networks of concepts developed by the historians of ideas themselves. (ii) Data Organisation. Interpretive models in our sense must be seen as topic-specific knowledge organisation systems (KOS) implementable (i.e. formalisable) as e.g. computer science ontologies. We thus require historians of ideas to provide explicitly structured semantic framing of domain knowledge before investigating texts computationally, and to constantly re-input findings from the interpretive point of view. In this way, a computational history of ideas maximally profits from computer methods while also keeping humanities experts in the loop. We elucidate our proposal with reference to a model of the notion of axiomatic science in 18th -19th century Europe. (shrink)

We propose a new method for the history of ideas that has none of the shortcomings so often ascribed to this approach. We call this method the model approach to the history of ideas. We argue that any adequately developed and implementable method to trace continuities in the history of human thought, or concept drift, will require that historians use explicit interpretive conceptual frameworks. We call these frameworks models. We argue that models enhance the comprehensibility of historical texts, and provide (...) historians of ideas with a method that, unlike existing approaches, is susceptible neither to common holistic criticisms nor to Skinner's objections that the history of ideas yields arbitrary and biased reconstructions. To illustrate our proposal, we discuss the so-called Classical Model of Science and draw upon work in computer science and cognitive psychology. (shrink)

I agree with Robbert Van den Berg that Plotinus endorses Socratic intellectualism, but I challenge his view that Plotinus rejects the phenomenon of akrasia. According to Van den Berg, the only form of akrasia acknowledged by Plotinus is a conditional, or ‘weak,’ akrasia. I provide some reasons for thinking that Plotinus might have accepted complete or ‘strong’ akrasia—full stop. While such strong forms of akrasia are usually taken to conflict with Socratic intellectualism, I argue that Plotinus’s complex, dual-self (...) psychology allows a way in which he, unique among ancient philosophers, could simultaneously endorse Socratic intellectualism and hard akrasia. (shrink)

We argue that an adequate treatment of verb phrase anaphora must depart in two major respects from the standard approaches. First of all, VP anaphors cannot be resolved by simply identifying the anaphoric VP with an antecedent VP. The resolution process must establish a syntactic/semantic parallelism between larger units that the VPs occur in. Secondly, discourse structure has a significant influence on the reference possibilities of VPA. This influence must be accounted for. We propose a treatment which meets these requirements. (...) It builds on a discourse grammar which characterizes discourse cohesion by means of a syntactic/semantic matching procedure which recognizes parallel structures in discourse. It turns out that this independently motivated procedure yields the resolution of VPA as a side effect. (shrink)

The step to e-research in philosophy depends on the availability of high quality, easily and freely accessible corpora in a sustainable format composed from multi-language, multi-script books from different historical periods. Corpora matching these needs are at the moment virtually non-existing. Within @PhilosTei, we have addressed this corpus building problem by developing an open source, web-based, user-friendly workflow from textual images to TEI, based on state-of-the-art open source OCR software, to wit Tesseract, and a multi-language version of TICCL, a powerful (...) OCR post-correction tool. We have demonstrated the utility of the tool by applying it to a multilingual, multi-script corpus of important eighteenth to twentieth-century European philosophical texts. (shrink)

HENDRIK VAN DEN BERG argues that Rand's claim that evidence of capitalism's success is "incontrovertible" cannot be confirmed using familiar annual GDP per capita figures. This article argues that annual GDP per capita cannot logically represent individual welfare because it measures an annual income flow while individuals judge their welfare by their lifetime income. Data are available to measure an economy's capacity to enhance individual lifetime welfare. Not only does this measure come closer to Rand's focus on the individual, (...) it also suggests that the past 200 years of capitalist development have raised individual welfare even more than the familiar, but misleading, annual GDP measures show. (shrink)

Recently, the second author, Briseid, and Safarik introduced nonstandard Dialectica, a functional interpretation capable of eliminating instances of familiar principles of nonstandard arithmetic—including overspill, underspill, and generalizations to higher types—from proofs. We show that the properties of this interpretation are mirrored by first-order logic in a constructive sheaf model of nonstandard arithmetic due to Moerdijk, later developed by Palmgren, and draw some new connections between nonstandard principles and principles that are rejected by strict constructivism. Furthermore, we introduce a variant of (...) the Diller–Nahm interpretation with two different kinds of quantifiers, similar to Hernest’s light Dialectica interpretation, and show that one can obtain nonstandard Dialectica by weakening the computational content of the existential quantifiers—a process called herbrandization. We also define a constructive sheaf model mirroring this new functional interpretation, and show that the process of herbrandization has a clear meaning in terms of these sheaf models. (shrink)