This thesis examines possible philosophies to account for the practice of mathematics, exploring the metaphysical, ontological, and epistemological outcomes of each possible theory. Through a study of the two most probable ideas, mathematical platonism and fictionalism, I focus on the compelling argument for platonism given by an appeal to the sciences. The Indispensability Argument establishes the power of explanation seen in the relationship between mathematics and empirical science. Cases of this explanatory power illustrate how we might have reason to believe in the existence of mathematical entities present within our best scientific theories. The second half of this discussion surveys Newtonian Cosmology and other inconsistent theories as they pose issues that have received insignificant attention within the philosophy of mathematics. The application of these inconsistent theories raises questions about the effectiveness of mathematics to model physical systems.

Introduction: I lay out the broad contours of my thesis: a defence of mathematical nominalism, and nominalism more generally. I discuss the possibility of metaphysics, and the relationship of nominalism to naturalism and pragmatism. Chapter 2: I delineate an account of abstractness. I then provide counter-arguments to claims that mathematical objects make a di erence to the concrete world, and claim that mathematical objects are abstract in the sense delineated. Chapter 3: I argue that the epistemological problem with abstract objects is not best understood as an incompatibility with a causal theory of knowledge, or as an inability to explain the reliability of our mathematical beliefs, but resides in the epistemic luck that would infect any belief about abstract objects. To this end, I develop an account of epistemic luck that can account for cases of belief in necessary truths and apply it to the mathematical case. Chapter 4: I consider objections, based on (meta)metaphysical considerations and linguistic data, to the view that the existential quantifier expresses existence. I argue that these considerations can be accommodated by an existentially committing quantifier when the pragmatics of quantified sentences are properly understood. I develop a semi-formal framework within which we can define a notion of nominalistic adequacy. I show how our notion of nominalistic adequacy can show why it is legitimate for the nominalist to make use of platonistic “assumptions” in inference-making. Chapter 5: I turn to the application of mathematics in science, including explanatory applications, and its relation to a number of indispensability arguments. I consider also issues of realism and anti-realism, and their relation to these arguments. I argue that abstraction away from pragmatic considerations has acted to skew the debate, and has obscured possibilities for a nominalistic understanding of mathematical practices. I end by explaining the notion of a pragmatic meta-vocabulary, and argue that this notion can be used to carve out a new way of locating our ontological commitments. Chapter 6: I show how the apparatus developed in earlier chapters can be utilised to roll out the nominalist project to other domains of discourse. In particular, I consider propositions and types. I claim that a unified account of nominalism across these domains is available. Conclusion: I recapitulate the claims of my thesis. I suggest that the goal of mathematical enquiry is not descriptive knowledge, but understanding.

Thesis advisor: Patrick Byrne / In the late 19th century, Georg Cantor opened up the mathematical field of set theory with his development of transfinite numbers. In his radical departure from previous notions of infinity espoused by both mathematicians and philosophers, Cantor created new notions of transcendence in order to clearly described infinities of different sizes. Leading the opposition against Cantor's theory was Leopold Kronecker, Cantor's former mentor and the leading contemporary German mathematician. In their lifelong dispute over the transfinite numbers emerge philosophical disagreements over mathematical existence, consistency, and freedom. This thesis presents a short summary of Cantor's controversial theories, describes Cantor and Kronecker's philosophical ideas, and attempts to state clearly their differences of opinion. In the end, the author hopes to present the shock caused by Cantor's work and an appreciation of the two very different philosophies of mathematics represented by Cantor and Kronecker. / Thesis (BA) — Boston College, 2005. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Philosophy. / Discipline: College Honors Program.

In this thesis I argue forin re structuralism in the philosophy of mathematics. In the first chapters of the thesis I argue that there is a genuine epistemic access problem for Platonism, that the semantic challenge to nominalism may be met by paraphrase strategies, and that nominalizations of scientific theories have had adequate success to blunt the force of the indispensability argument for Platonism. In the second part of the thesis I discuss the development of logicism and structuralism as methodologies in the history of mathematics. The goal of this historical investigation is to lay the groundwork for distinguishing between the philosophical analysis of the content of mathematics and the analysis of the breadth and depth of results in mathematics. My central contention is that the notion of logical structure provides a context for the latter not the former. In turn, this contention leads to a rejection of ante rem structuralism in favor of in re structuralism. In the concluding part of the dissertation the philosophy of mathematical structures developed and defended in the preceding chapters is applied to the philosophy of science.

As early as 1958 John McCarthy stressed the importance of formulating common sense knowledge, and common sense reasoning, in a rigourous manner. Today, this is considered to be the central problem in Artificial Intelligence (AI). A strong advocate of this view is Patrick Hayes, who in 1974 argued that fuzzy logic was not a useful mechanism for representing vague terms, and suggested a better formalism could be developed using Zeeman's Tolerance Geometry. Five years later, Hayes complained about AI's emphasis on toy world's and suggested that a suitable project would be to formalise our common sense knowledge of the (everyday) physical world. A project now known as Naïve Physics (NP). In this project, Hayes discussed his attempts at describing the intuitive notion of objects touching using topological techniques, and indicated that Tolerance Geometry would be a better framework for capturing this notion. This thesis investigates Hayes' suggestion of developing Tolerance Geometry into a formal framework in which one can capture such intuitive terms as bodies touching, and characterising such vague terms as being tall. The analysis in this thesis begins with a (formal) investigation of the Sorites paradox. This puzzle is singled out because it clearly illustrates the problems raised by any formal analysis of vagueness in any language. The analyses of vagueness indicate that vague predicates possess continuous interpretations, and thence demonstarte the need for a spatial structure to be incorporated into the formalised metalanguage. This metalanguage then provides the framework for the proof that the Sorites is insoluble in a logic with a truth-set given by {0,1}, but consistent in a logic with truth-set given by {0,u,1}. Furthermore, this investigation reveals that Zadeh has confused the notions of continuity and the continuum, and therefore his theory of fuzzy sets rest on a mistaken assumption.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:24:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-13Bitstream added on 2014-06-13T19:31:59Z : No. of bitstreams: 1 barbosa_g_me_rcla.pdf: 822152 bytes, checksum: da920714b1e5049412e0666e10a1de1f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo dessa pesquisa é participar da discussão acerca das diferentes concepções de Platão e Aristóteles a respeito da natureza e do estatuto ontológico dos entes matemáticos. Enquanto Platão situa o âmbito ontológico dos entes matemáticos entre dois mundos, o sensível e o inteligível, Aristóteles nega o caráter supra-sensível dos objetos matemáticos e oferece como resposta a sua filosofia empirista da matemática. Aristóteles teria dirigido duras críticas contra Platão e os acadêmicos nos dois últimos livros da Metafísica, M e N, respectivamente. Desde a antiguidade, vários autores sustentam que tais críticas referem-se às “doutrinas não-escritas” de Platão, que seriam cursos por ele ministrados na Academia, cujo teor ele não quis escrever por considerar que somente à dialética oral caberia o ensinamento dos primeiros princípios. Utilizando uma metodologia de pesquisa filosófica e também a história da filosofia e da matemática, foram abordados diversos textos, que vão desde livros e artigos atuais, até as próprias obras de Platão e Aristóteles relacionadas ao tema. Como parte das reflexões finais, o presente trabalho destaca a importância da exegese para uma correta interpretação das filosofias da matemática de Platão e Aristóteles e ainda das relações entre elas. / The research aim is the discussion about Plato and Aristotle’s different conceiving about the nature and the ontological status of mathematical entities. While Plato located the ontological scope of mathematical entities between two worlds, the sensible and the intelligible, Aristotle denies the character “super-sensible” of the mathematical entities and offers in response his own empiricist philosophy of mathematics. Aristotle would have direct harsh criticism to Plato and the academics in two last books of his Metaphysics, M and N, respectively. Since ancient times several authors argue that these criticism refer to “unwritten doctrines” of Plato, that they would be courses that he taught at the Academy, whose contents he did not want to write because he had believe that only oral dialectic should teach the first principles. Using a philosophical methodology of research and also the history of philosophy and mathematics several texts were discussed, like current books and articles as well as works of Plato and Aristotle about the theme. As part of final reflection, the present work highlights the exegesis importance for a correct interpretation of the mathematics philosophy from Plato and Aristotle and even the relationships between them.

My thesis is an exposition and defence of Aristotle's philosophy of mathematics. The first part of my thesis is an exposition of Aristotle's cryptic and challenging view on mathematics and is based on remarks scattered all over the corpus aristotelicum. The thesis' central focus is on Aristotle's view on numbers rather than on geometrical figures. In particular, number is understood as a countable plurality and is always a number of something. I show that as a consequence the related concept of counting is based on units. In the second part of my thesis, I verify Aristotle's view on number by applying it to his account of time. Time presents itself as a perfect test case for this project because Aristotle defines time as a kind of number but also considers it as a continuum. Since numbers and continuous things are mutually exclusive this observation seems to lead to an apparent contradiction. I show why a contradiction does not arise when we understand Aristotle properly. In the third part, I argue that the ontological status of mathematical objects, dubbed as materially [hulekos, ÍlekÀc] by Aristotle, can only be defended as an alternative to Platonism if mathematical objects exist potentially enmattered in physical objects. In the fourth part, I compare Aristotle's and Plato's views on how we obtain knowledge of mathematical objects. The fifth part is an extension of my comparison between Aristotle's and Plato's epistemological views to their respective ontological views regarding mathematics. In the last part of my thesis I bring Frege's view on numbers into play and engage with Plato, Aristotle and Frege equally while exploring their ontological commitments to mathematical objects. Specifically, I argue that Frege should not be mistaken for a historical Platonist and that we find surprisingly many similarities between Frege and Aristotle. After having acknowledged commonalities between Aristotle and Frege, I turn to the most significant differences in their views. Finally, I defend Aristotle's abstractionism in mathematics against Frege's counting block argument. This whole project sheds more light on Aristotle's view on mathematical objects and explains why it remains an attractive view in the philosophy of mathematics.

My dissertation focuses on mathematical explanation found in proofs looked at from a historical point of view, while stressing the importance of mathematical practices. Current philosophical theories on explanatory proofs emphasize the structure and content of proofs without any regard to external factors that influence a proof’s explanatory power. As a result, the major philosophical views have been shown to be inadequate in capturing general aspects of explanation. I argue that, in addition to form and content, a proof’s explanatory power depends on its targeted audience. History is useful here, because from it, we are able to follow the transition from a first-generation proof, which is usually non-explanatory, into its explanatory version. By tracking the similarities and differences between these proofs, we are able to gain a better understanding of what makes a proof explanatory according to mathematicians who have the relevant background to evaluate it as so. My first chapter discusses why history is important for understanding mathematical practices. I describe two kinds of history: one that presents a narrative of events, which influenced developments in mathematics both directly and indirectly, and another, typically used in mathematical research, which concentrates only on technical developments. I contend that both versions of the past benefit the philosopher. History used in research gives us an idea of what mathematicians desire or find to be important, while history written by historians shows us what effects these have on mathematical practices. The next two chapters are about explanatory proofs. My second chapter examines the main theories of mathematical explanation. I argue that these theories are short-sighted as they only consider what appears in a proof without considering the proof’s purported audience or background knowledge necessary to understand the proof. In the third chapter, I propose an alternative way of analyzing explanatory proofs. Here, I suggest looking at a theorem’s history, which includes its successive proofs, as well as the mathematicians who wrote them. From this, we can better understand how and why mathematicians prove theorems in multiple ways, which depends on the purposes of these theorems. The last chapter is a case study on the computer proof of the Four Color Theorem by Appel and Haken. Here, I compare and contrast what philosophers and mathematicians have had to say about the proof. I argue that the main philosophical worry regarding the theorem—its unsurveyability—did not make a strong impact on the mathematical community and would have hindered mathematical development in computer-assisted proofs. By studying the history of the theorem, we learn that Appel and Haken relied on the strategy of Kempe’s flawed proof from the 1800s (which, obviously, did not involve a computer). Two later proofs, also aided by computer, were developed using similar methods. None of these proofs are explanatory, but not because of their massive lengths. Rather, the methods used in these proofs are a series of calculations that exhaust all possible configurations of maps.

Ever since the advent of computerized methods for solving mathematical problems, the concept of surveyability has played a central role in the debate surrounding what constitutes a mathematical proof. Ordinarily, it is by surveying the argument presented that the mathematician ascertains the truth of the conclusion, but with the advent of computer assisted technologies, there are mathematical conclusions known to be true without anyone ever having been able to survey the argument in its entirety. What this seems to suggest is that what is called "mathematical knowledge" encompasses two different types of knowledge: one gained through the act of surveying a proof, and the other through computerized empirical experiments. The goal of this thesis is to investigate the connection between surveyability and the acquisition of mathematical knowledge, thereby elucidating the difference between the two epistemological categories. The claim is that this can be accomplished by applying Heidegger's account of unconcealment to the notion of mathematical truth, supported by a Wittgensteinian analysis of the act of surveying as a type of reproduction of the proof. While much has been written on how his early mathematical training influenced Heidegger's philosophy, attempts at applying elements from his thinking to problems belonging to the philosophy of mathematics are rare. This investigation has the ambition of making a convincing case for the potential in this kind of approach.