The Kinds of Mathematical Objects is an exploration of the taxonomy of the mathematical realm and the metaphysics of mathematical objects. I defend antireductionism about cardinals and ordinals: the view that no cardinal number and no ordinal number is a set. Instead, I suggest, cardinals and ordinals are sui generis abstract objects, essentially linked to specific abstraction functors (higher-order functions corresponding to operators in abstraction principles). Sets, in contrast, are not essentially values of abstraction functors: the best explanation of the nature of sethood is given by a variation on the standard iterative account. I further defend the theses that no cardinal number is an ordinal number and that the natural numbers are, as Frege maintained, all and only the finite cardinal numbers. My case for these conclusions relies not on the well-known antireductionist argument developed by Paul Benacerraf, but on considerations about ontological dependence. I argue that, given generally accepted principles about the dependence of a set on its elements, ordinal and cardinal numbers have dependence profiles that are not compatible with any version of set-theoretic ontological reductionism. In addition, a formal framework for set theory with sui generis abstract objects is developed on a type-theoretical basis. I give a philosophical defence of the choice of type theory and discuss various questions relating to the nature of its models.

This thesis confronts Penelope Maddy's Second Philosophical study of set theory with a philosophical analysis of a part of contemporary set-theoretic practice in order to argue for three features we should demand of our philosophical programmes to study mathematics. In chapter 1, I argue that the identification of such features is a pressing philosophical issue. Chapter 2 presents those parts of the discursive reality the set theorists are currently in which are relevant to my philosophical investigation of set-theoretic practice. In chapter 3, I present Maddy's Second Philosophical programme and her analysis of set-theoretic practice. In chapters 4 and 5, I philosophically investigate contemporary set-theoretic practice. I show that some set theorists are having a debate about the metaphysical status of their discipline{ the pluralism/non-pluralism debate{ and argue that the metaphysical views of some set theorists stand in a reciprocal relationship with the way they practice set theory. As I will show in chapter 6, these two stories are disharmonious with Maddy's Second Philosophical account of set theory. I will use this disharmony to argue for three features that our philosophical programmes to study mathematics should have: they should provide an anthropology of mathematical goals; they should account for the fact that mathematical practices can be metaphysically laden; they should provide us with the means to study contemporary mathematical practices.

Made available in DSpace on 2016-04-27T16:57:42Z (GMT). No. of bitstreams: 1 tese_luzia_aparecida_palaro.pdf: 27255885 bytes, checksum: d2ee8521118c71c7bfe212a84a1dfc70 (MD5) Previous issue date: 2006-05-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main aim of this study was to consider the aspects which characterises Henri Lebesgue s conception of Mathematics Education. Lebesgue (1875-1941), as well as being one of the most eminent mathematicians of the twentieth century and revolutionising Mathematical Analysis with the creation of a new theory of measure and hence a new definition of the integral, was also a extremely dedicated teacher. Concerned about teacher education, he contributed much to debates on didactical, historical and philosophical issues related to Mathematics. The methodology adopted for this study was based on research with a bibliographic character, with a historic-descriptive approach employed, beginning with a brief presentation of the life and works of Lebesgue. Following this, a historicphilosophical contextualisation of Mathematics of his epoch is presented, along with a description of the philosophy of Mathematics he defended. To highlight the originality of Lebesgue s mathematical practices, a study of the historical development of Calculus from the seventeenth century until his time is presented, with the theory of functions serving as the leading thread of this development. Using as a basis this historical development, a study is made of how some Calculus and Analysis textbooks define Integration and how they approach the Fundamental Theorem of Calculus. Finally, a study of the work About the Measure of Magnitude is presented, which identifies aspects of the process that Lebesgue proposed for the teaching of mathematics. The study concludes that Lebesgue, given his constructivist stance: was not keen in the axiomatic tendency that characterised the practice of Mathematics during his time; that he placed emphasis on activity considering Mathematics as a tool without its own objects: that he defended a philosophy of Mathematics as simple and utilitarian, which would be a mere report on the practices of mathematician: and that he believed that teaching like the practice of Mathematicians, should begin with an activity which could be used as the basis from which to abstract concepts and make generalization, leaving the axiomatic definitions until the end / O objetivo geral deste trabalho foi levantar os aspectos caracterizadores da concepção de Educação Matemática de Henri Lebesgue (1875-1941), que além de ter sido um dos mais eminentes matemáticos do século XX pois revolucionou a Análise Matemática com a criação de uma nova teoria da medida e, fundamentado nesta, uma nova definição de integral , foi também um professor extremamente dedicado e que se preocupava com a formação de professores e, muito contribuiu para os assuntos didáticos, históricos e filosóficos da Matemática. A metodologia do estudo baseou-se em uma pesquisa de caráter bibliográfico, sob a abordagem histórico-descritiva; iniciando-se com uma breve apresentação da vida e das obras de Lebesgue. Em seguida, foram apresentadas uma contextualização histórico-filosófica da Matemática de sua época e a filosofia da Matemática que propagava. Buscando realçar a originalidade de Lebesgue, pela sua forma de fazer Matemática, foi apresentado um estudo do desenvolvimento histórico do Cálculo, do século XVII até Lebesgue, sendo a teoria das funções o fio condutor desse desenvolvimento. Tendo como base este desenvolvimento histórico, é apresentado um estudo de como alguns livros didáticos de Cálculo e Análise definem a integração e como abordam o Teorema Fundamental do Cálculo, identificando assim, a perspectiva adotada. Por fim, é apresentado um estudo da obra Sobre a Medida das Grandezas de autoria de Lebesgue, buscando identificar aspectos do processo que Lebesgue considerava para o ensino da Matemática. O estudo concluiu que Lebesgue, construtivista que era, não gostava da tendência axiomática de fazer Matemática de sua época; dava ênfase a atividade e considerava a Matemática um instrumento que não tem objetos próprios; propagava uma filosofia da Matemática simples e utilitária, que seria apenas um relato das práticas desenvolvidas pelos matemáticos; considerava que, no ensino assim como na prática de fazer matemática, se deveria iniciar com uma atividade, a partir da qual poderiam ser abstraídos conceitos, fazer generalizações, deixando as definições axiomáticas por último