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The first of its kind, this book presents a widely accessible exposition of topos theory, aimed at the philosopher-logician as well as the mathematician. It is suitable for individual study or use in class at the graduate level (it includes 500 exercises). It begins with a fully motivated introduction to category theory itself, moving always from the particular example to the abstract concept. It then introduces the notion of elementary topos, with a wide range of examples and goes on to develop its theory in depth, and to elicit in detail its relationship to Kripke's intuitionistic semantics, models of classical set theory and the conceptual framework of sheaf theory (``localization'' of truth). Of particular interest is a Dedekind-cuts style construction of number systems in topoi, leading to a model of the intuitionistic continuum in which a ``Dedekind-real'' becomes represented as a ``continuously-variable classical real number''. The second edition contains a new chapter, entitled Logical Geometry, which introduces the reader to the theory of geometric morphisms of Grothendieck topoi, and its model-theoretic rendering by Makkai and Reyes. The aim of this chapter is to explain why Deligne's theorem about the existence of points of coherent topoi is equivalent to the classical Completeness theorem for ``geometric'' first-order formulae.

Quasitopoi generalize topoi, a concept of major importance in the theory of Categoreis, and its applications to Logic and Computer Science. In recent years, quasitopoi have become increasingly important in the diverse areas of Mathematics such as General Topology and Fuzzy Set Theory. These Lecture Notes are the first comprehensive introduction to quasitopoi, and they can serve as a first introduction to topoi as well.

Traditionen leben von der Dialektik der Wiederholung, die das Gleiche stets anders inszeniert. Sie speisen sich aus den Erinnerungen; an der Grenze von bedacht und selbstverständlich getan lassen sie sich nur als selbstverständliche Überzeugungen bestimmen. Aber wie ist es dennoch möglich, Traditionen zu beeinflussen? Der vorliegende Band widmet sich der Frage, wie man mit Traditionen Symbolpolitik machen kann. Was sind die Zumutungen der Traditionen, wenn sie politisch instrumentalisiert werden? Gibt es Grenzen der Manipulation, die im Wesen der jeweiligen Traditionen liegen und sie folglich definieren? Die BeiträgerInnen geben eine Vielzahl von Antworten, indem sie sich Topoi aus Mittelalter und Früher Neuzeit aus interdisziplinärer Perspektive widmen. Traditions thrive on the dialectic of repetition. Drawing their topoi from the well of memory, they are situated on the very border between the deliberate and the habitual. Yet how is it possible to influence traditions? The present collection of essays studies the ways in which traditions are employed in the service of symbolic politics. What are the burdens and impositions of traditions, when their topoi are consciously exploited in the service of ideological purposes? Are there certain limits to manipulation that lie in the very nature of the traditions in question, a nature which therefore defines them? The contributors give a host of answers, studying topoi in medieval and early modern Europe from an interdisciplinary perspective.

This monograph presents a new, systematic treatment of the relation between classifying topoi and classifying spaces of topological categories. Using a new generalized geometric realization which applies to topoi, a weak homotopy equival- ence is constructed between the classifying space and the classifying topos of any small (topological) category. Topos theory is then applied to give an answer to the question of what structures are classified by "classifying" spaces. The monograph should be accessible to anyone with basic knowledge of algebraic topology, sheaf theory, and a little topos theory.

A classic introduction to mathematical logic from the perspective of category theory, this text is suitable for advanced undergraduates and graduate students and accessible to both philosophically and mathematically oriented readers. Its approach moves always from the particular to the general, following through the steps of the abstraction process until the abstract concept emerges naturally. Beginning with a survey of set theory and its role in mathematics, the text proceeds to definitions and examples of categories and explains the use of arrows in place of set-membership. The introduction to topos structure covers topos logic, algebra of subobjects, and intuitionism and its logic, advancing to the concept of functors, set concepts and validity, and elementary truth. Explorations of categorial set theory, local truth, and adjointness and quantifiers conclude with a study of logical geometry.

A Collection of Lectures by Variuos Authors

This work provides some interesting new results on the notion of the topos and the theory of hypothetical syllogisms in Aristotle based on an incisive interpretation of Aristotle's "Topics" and certain passages of the "Analytics."

"In Topoi/Graphein Christian Abrahamsson maps the paradoxical limit of the in-between to revealthat to be human is to know how tolive with the difference between the known and the unknown. Using filmic case studies, including CodeInconnu, Lord of the Flies, and Apocalypse Now,and focusing on key concerns developed in the works of the philosophers Deleuze, Olsson, and Wittgenstein, Abrahamsson starts within the notion of fixed spatiality, in whichhuman thought and action are anchored in the given of identity. He then movesthrough a social world in which spatiotemporal transformations are neitherfixed nor taken for granted. Finally he edges into the pure temporality that liesbeyond the maps of fixed points and social relations. Each chapter is organized into two subjects: topoi, orexcerpts from the films, and graphein, the author's interpretation ofpresented theoriesto mirror the displacements,transpositions, juxtapositions, fluctuations, and transformations between delimited categories. A landmark work in the study of human geography, Abrahamsson's book proposes that academic and intellectual attention should focus on the spatialization between meaning and its materialization in everyday life."