Logik vid Göteborgs Universitet

OBS Ny sida för logikseminariet.

Ungefärligen varannan fredag förmiddag träffas filosofiska et cetera institutionens logikseminarium. Seminariet riktar sig till c/d-studenter, doktorander, lärare och forskare i logik, men även till intresserade från andra ämnen. Vi varvar arbetsseminarier, då egna texter presenteras, med seminarier av fördjupande eller mer allmänbildande karaktär.

Det finns en epostlista som alla intresserade kan anmäla sig till. Information om nästkommande seminarium skickas ut en knapp vecka i förväg. Listan har adress logik@listserv.hum.gu.se

Tid: 10:15 - 12:00
Plats: T116 (OBS ny lokal), Gamla Hovrätten Olof Wijksgatan 6, om inte annat meddelas. Lokalen ligger i gatuplanet; genom huvudingången, rakt fram, sedan till vänster och längst bort i korridoren
Det finns ett arkiv för äldre seminarier. Vill du prata på seminariet eller har du förslag på talare? Hör då av dig till logic@gu.se.

Vårterminen 2010

• 29/1: Palle Leth Frege om predikatreferens
  Freges tes att predikattermer har Bedeutung anses allmänt vara djupt problematisk. De flesta anser att Freges grund för tesen var hans övertygelse om att relationen mellan predikat och begrepp är analog med relationen mellan egennamn och objekt. Jag hoppas visa på att Freges texter i frågan inte ger något stöd för uppfattningen att en sådan analogi ligger till grund för hans tes att predikat har Bedeutung.
• 12/2: Ulf Persson Platonism and Mathematics
  For some reason Platonism is considered something of a dirty word in philosophy, a symptom of rigid naivity, and something people rather distance themselves from even if they advocate ideas essentially congruent with it. In the seminar I intend to champion mathematical Platonism in its interpretation as mathematical realism and discuss how to distinguish between the transhuman and human elements in mathematics, the failure of which I believe is the basis for much confusion that characterizes the ongoing debate. The talk is going to be predominantly speculative and philosophical in nature.
• 26/2: Denis Bonnay Modeling Inexact Knowledge
  Perceptual indiscriminability is typically intransitive. Given three shades of color a, b and c, it can well be the case that I am not able to distinguish between a and b on the one hand, b and c on the other hand, even though I can distinguish between a and c. In this talk, I will discuss two issues regarding this basic fact.

  1) How does intransitivity impact the logic of (perceptual) knowledge? If perceptual indiscriminability is directly taken to generate an accessiblity relation between epistemic alternatives, intransitivity will yield failure of positive introspection: my knowing that p is not sufficient for my knowing that I know p.

  2) Where does intransitivity come from? Telling whether two shades or color are identical or categorizing a shade of color as orange or red can be construed as a decision task. Why does decision lead to intransitivity? Can we build psychologically plausible models of the inexactness of our perceptual knowledge.

  In connection with 1), I will argue that introspection can be recovered on intransitive models. In connection with 2), I will show how signal detection theory can provide the basis for fine-grained logical models.

  The talk is based on a series of papers co-authored with Paul Egré. In particular,

  "Knowing one's limits", to appear in Dynamic Epistemology: Contemporary Perspectives, O. Roy, P. Girard and M. Marion (eds) (accesible online from here) and section 4 of "Vagueness, Uncertainty and Degrees of Clarity" forthcoming in Synthese (accesible online from there)

• 12/3: Jesper Carlström Formal logic in railway signalling applications
  Prover Technology AB applies formal logic to design and verification of railway signalling systems. The main product is Prover iLock, a Windows program with a graphical user interface that allows a signalling engineer to define a railyard by drawing tracks with the mouse, and then automatically generate an interlocking system that can also be formally verified in the same tool, or by an independent tool. I will outline the process and discuss the problems encountered when academic ideas meet the down-to-earth demands of our customers.

  (Jesper doktorerade i matematik (logik) för Per Martin-Löf vid Stockholms universitet. Han disputerade 2005 och är nu utvecklingsledare på Prover för logikspråket PiSPEC. Detta används för att specificera logiken i ställverkssystem.

• 26/3: Jan Smith Hume, Kant, Darwin, and the rules of logic
  Hume's crucial observation that there is no direct evidence for causality
  opens up for an evolutionary understanding of causality. I will also argue
  that in an evolutionary perspective, the rules of logic play a similar role
  as causality.I will not rely on any result in biology, except that the
  gene-centered view of evolution has in general broadened the scope of
  evolutionary explanations. Rather, I will corroborate my claims by Kant's
  view on causality and Aristotle's on the rules of logic.
• 9/4: Dag Westerståhl Compositionality and Context Dependence
  Does the fact that linguistic communication is strongly context-dependent constitute a threat to the idea that natural languages are compositional? To many, it clearly does. But what exactly is at stake here? In this talk I try -- after a brief introduction to compositionality -- to sort out some of the issues by (a) distinguishing different kinds of context dependence, (b) distinguishing different kinds of semantic values (meaning, content, extension, etc.) for which the issue of compositionality may arise, (c) noting that for many of these values, the concept of compositionality has to be adapted to the presence of contextual arguments, and that there are at least two different ways of doing this, and (d) explain the logical relations between the resulting notions of compositionality. I will also sketch an approach to linguistic context dependence (this is joint work with Peter Pagin), and as an illustration explain how it can be used to give a straightforward account of pure quotation which is compositional in the relevant sense.
• 30/4: Denis Bonnay The generality of logic and the problem of logical constants
  To account for our informal notion of logical consequence, it is not sufficient to provide a conceptually motivated definition of logical consequence. The definition of logical consequence has to be supplemented with a conceptually motivated division between logical symbols and extra-logical symbols. In connection with the problem of motivating this divide, the main aim of this talk is to investigate two related ideas. The first one is that being a possible interpretation for a logical constant amounts to satisfying some invariance criterion. The second one is that such a characterization can be vindicated by appealing to the generality of logic.

  I will present the first characterization of this kind given by Tarski himself in 1966, as a late follow-up to his 1936 paper on logical consequence. No matter how attractive the simplicity of Tarski's proposal is, the analysis of generality in terms of invariance has proven to be more involved than Tarski had thought. So I will develop on an objection to Tarski's analysis and recall an alternative characterization I have given which aims at fixing the problem. The corresponding invariance criterion has recently been challenged by Feferman in 2009. In the final part of the talk, I argue that Feferman's criticisms can be met by redesigning the framework for invariance. This is shown to yield an invariance characterization of first-order definable operations, which can be justified in terms of generality.

• 7/5: Aarne Ranta Logic, Semantics, Translation, and Universal Grammar
  That languages have a common semantical foundation in logic is an old idea. In a letter to Mersenne in 1629, Descartes proposed a universal formal language that would serve as the basis of translation between languages; this idea was developed further by Leibniz in his "characteristica universalis". In modern times, systems like UNL and SUMO are used as interlinguas for machine translation, much in the same spirit. On the other hand, critics like Sapir and Whorf have rejected the idea of a common semantical foundation of languages, and the main stream of machine translation is based on statistics on co-occurrences of words and phrases, with no reference to semantics; Google translate (http://translate.google.com) is an extremely successful example of this approach.

  In the talk, I will summarize the main arguments underlying the different approaches to translation. Then I will present an approach which, in a sense, builds on Descartes's idea of a universal formal language, but takes into account the criticisms. The key idea is to distinguish between different levels of abstraction in language: on some levels, translation is clearly impossible, whereas on some other levels, it is clearly possible and the problems are technical rather than philosophical. The approach has been proven in several applications, and it is currently developed further in the European project MOLTO (Multilingual On-Line Translation, http://www.molto-project.eu).

• 21/5: Fredrik Engström Borelkvantorer och logiska konstanter
  Jag kommer att introducera Borelkvantorer och ge några tekniska resultat som kan ses om generaliseringar av Lopez-Escobars sats om invarianta Borelmängder. Jag kommer också koppla dessa resultat med den pågående debatten om logiska konstanter.
• 4/6: CANCELED