In set theory, a maximality principle is a principle that asserts some maximality property of the universe of sets or some part thereof. Set theorists have formulated a variety of maximality principles in order to settle statements left undecided by current standard set theory. In addition, philosophers of mathematics have explored maximality principles whilst attempting to prove categoricity theorems for set theory or providing criteria for selecting foundational theories. This article reviews recent work concerned with the formulation, investigation and justification (...) of maximality principles. (shrink)

. Remarkably, despite the tremendous success of axiomatic set-theory in mathematics, logic and meta-mathematics, e.g., model-theory, two philosophical worries about axiomatic set-theory as the adequate catch of the set-concept keep haunting it. Having dealt with one worry in a previous paper in this journal, we now fulfil a promise made there, namely to deal with the second worry. The second worry is the Skolem Paradox and its ensuing Skolemite skepticism. We present a comparatively novel and simple analysis of the argument (...) of the Skolemite skeptic, which will reveal a general assumption concerning the meaning of the set-concept (we call it Connexion M). We argue that the Skolemite skeptics argument is a petitio principii and that consequently we find ourselves in a dialectical situation of stalemate.Few (if any) working set-theoreticians feel a tension – let alone see a paradox – between, on the one hand, what the Löwenheim–Skolem theorems and related results seem to be telling us about the set-concept, and, on the other hand, their uncompromising and successful use of the set-concept and their continuing enthusiasm about it, in other words: their lack of skepticism about the set-concept. Further, most (if not all) working settheoreticians have a relaxed attitude towards the ubiquitous undecidability phenomenon in set-theory, rather than a worrying one. We argue these are genuine philosophical problems about the practice of set-theory. We propound solutions, which crucially involve a renunciation of Connexion M. This breaks the dialectical situation of stalemate against the Skolemite skeptic. (shrink)

The paper exposes the philosophical and mathematical flaws in an attempt to settle the continuum problem by a new class of axioms based on probabilistic reasoning. I also examine the larger proposal behind this approach, namely the introduction of new primitive notions that would supersede the set theoretic foundation of mathematics.

Can a scientific naturalist be a mathematical realist? I review some arguments, derived largely from the writings of Penelope Maddy, for a negative answer. The rejoinder from the realist side is that the irrealist cannot explain, as well as the realist can, why a naturalist should grant the mathematician the degree of methodological autonomy that the irrealist's own arguments require. Thus a naturalist, as such, has at least as much reason to embrace mathematical realism as to embrace irrealism.

Öz: Frege özel adların (ve diğer dilsel simgelerin) anlamları ve gönderimleri arasında ünlü ayrımını yaptığı “Anlam ve Gönderim Üzerine” (1948) adlı makalesinde, bu ayrımın önemi, gerekliliği ve sonuçları üzerine uzun değerlendirmeler yapar ancak özel adın anlamından tam olarak ne anlaşılması gerektiğinden yalnızca bir dipnotta kısaca söz eder. Örneğin “Aristoteles” özel adının anlamının Platon’un öğrencisi ve Büyük İskender’in öğretmeni ya da Stagira’da doğan Büyük İskender’in öğretmeni olarak alınabileceğini söyler. Burada dikkat çeken nokta örnekteki özel adın olası anlamları olarak gösterilen belirli betimlemelerin (...) de özel ad içeriyor olması. Anlamın Frege için bileşimsel olduğu, bir başka deyişle bir dilsel simgenin anlamının (varsa) parçalarının anlamlarınca belirlendiği düşünülürse, örnekteki belirli betimlemelerin anlamlarının saptanabilmesi için içerdikleri özel adların da anlamları saptanıp betimleme içinde geçtikleri yere konmalıdır. Bu işlem hiçbir özel ad kalmayana kadar sürdürülmelidir. Ancak biraz düşünülünce bir özel adın nesnesini tekil olarak betimleyecek ve içinde özel ad geçmeyecek bir betimleme bulmanın kolay olmadığı görülür. Örneğin yukarıdaki betimlemelerde geçen “Platon”, “Büyük İskender” ve “Stagira” gibi özel adların anlamları olabilecek ancak özel ad içermeyen betimlemeler bulmak pek kolay görünmüyor. Ortaya bir sonsuz gerileme sorunu çıkmış gibi duruyor. Frege’nin anlam-gönderim ayrımını için ciddi sonuçları olabilecek bu sorunu Frege çözebilir mi? Bu yazıda bu sorunun yanıtını arayacağım. Sorunu betimledikten sonra Frege’nin önündeki seçenekleri (örneğin bağlama duyarlı terimlerden (gösterme adılları veya belirteçler) yararlanma veya bağlamı sınırlama gibi) değerlendireceğim. -/- Abstract: In his “Sense and Reference” (1948), Frege makes his famous distinction between the sense and the reference of a proper name (and other signs) and discusses at length the significance, necessity and consequences of the distinction, but he explains how the sense of a proper name should be understood very briefly in a footnote. According to him, for example, the sense of the proper name “Aristotle” can be taken as the pupil of Plato and teacher of Alexander the Great or the teacher of Alexander the Great who was born in Stagira. What is interesting here is that the definite descriptions given as the possible senses of this proper name do themselves contain proper names too. Since the sense is something compositional for Frege, which means the sense of a linguistic sign is determined by its constituents (if there are any), in order to determine the sense of definite descriptions in question, we should first determine the senses of proper names they contain and substitute these senses with the proper names themselves. This process should continue until no proper name remains. However, it does not seem easy to find a definite description which describes the object of a proper name uniquely but contains no proper name itself. For instance, could we find appropriate senses that contain no proper name for “Plato”, “Alexander the Great” and “Stagira”? It does not seem likely. A problem of infinite regress appears to arise. Can Frege solve this problem, which poses a serious threat for his sensereference distinction? I will explore this problem in this paper. After explaining the problem, I will discuss the options (e.g. turning to indexicals or context restriction) Frege can take to deal with it. (shrink)

Despite some discomfort with this grandly philosophical topic, I do in fact hope to address a venerable pair of philosophical chestnuts: mathematical truth and existence. My plan is to set out three possible stands on these issues, for an exercise in compare and contrast.' A word of warning, though, to philosophical purists (and perhaps of comfort to more mathematical readers): I will explore these philosophical positions with an eye to their interconnections with some concrete issues of set theoretic method.

Mathematical naturalism forbids philosophical interventions in mathematical practice. This principle, strictly construed, places severe constraints on legitimate philosophizing about mathematics; it is also arguably incompatible with mathematical realism. One argument for the latter conclusion charges the realist with inability to take a truly naturalistic view of the Gödel Program in set theory. This argument founders on the disagreement among mathematicians about that program's prospects for success. It also turns out that when disagreements run this deep it is counterproductive to take (...) too narrow a view of how philosophers of mathematics may legitimately proceed. (shrink)

The purpose of this article is to explain why I believe that the Continuum Hypothesis (CH) is not a definite mathematical problem. My reason for that is that the concept of arbitrary set essential to its formulation is vague or underdetermined and there is no way to sharpen it without violating what it is supposed to be about. In addition, there is considerable circumstantial evidence to support the view that CH is not definite.

Putnam’s model-theoretic arguments for the indeterminacy of reference have been taken to pose a special problem for mathematical languages. In this paper, I argue that if one accepts that there are theory-external constraints on the reference of at least some expressions of ordinary language, then Putnam’s model-theoretic arguments for mathematical languages don’t go through. In particular, I argue for a kind of descriptivism about mathematical expressions according to which their reference is “anchored” in the reference of expressions of ordinary language. (...) These anchors add enough to the content of mathematical expressions to forestall the radical kind of indeterminacy that model-theoretic arguments are purported to show, while still leaving room for a plausible, moderate kind of indeterminacy. (shrink)

The article deals with the question of in which sense the notion of explanation can be applied to Kurt Gödel’s philosophy of mathematics. Gödel, as a mathematical realist, claims that in mathematics we are dealing with facts that have an objective character. One of these facts is the solvability of all well-formulated mathematical problems—and this fact requires a clarification. The assumptions on which Gödel’s position is based are: metaphysical realism: there is a mathematical universe, it is objective and independent of (...) us; epistemological optimism: we are equipped with sufficient cognitive power to gain insight into the universe. Gödel’s concept of a solution to a mathematical problem is much broader than of a mathematical proof—it is rather about finding reliable axioms that lead to a solution of the problem. I analyse the problem presented in the article, taking as an example the continuum hypothesis. (shrink)

Artykuł dotyczy zagadnienia, w jakim sensie można stosować kategorię wyjaśnienia do interpretacji filozofii matematyki Kurta Gödla. Gödel – jako realista matematyczny – twierdzi bowiem, że w wypadku matematyki mamy do czynienia z niezależnymi od nas faktami. Jednym z owych faktów jest właśnie rozwiązywalność wszystkich dobrze postawionych problemów matematycznych – i ten fakt domaga się wyjaśnienia. Kluczem do zrozumienia stanowiska Gödla jest identyfikacja założeń, na których się opiera: metafizyczny realizm: istnieje uniwersum matematyczne, ma ono charakter obiektywny, niezależny od nas; optymizm epistemologiczny: (...) jesteśmy wyposażeni w wystarczająco dobre środki poznawcze, aby uzyskać wgląd w owo uniwersum. Pojęcie rozwiązania problemu matematycznego Gödel rozumie znacznie szerzej niż jako podanie matematycznego dowodu – chodzi raczej o znalezienie wiarogodnych aksjomatów, prowadzących do rozwiązania. Stawiany w artykule problem analizuję na przykładzie hipotezy kontinuum. (shrink)