There is a large philosophical literature focused on what sorts of things can be said to exist. This field is called ontology. Ontological disputes have sometimes been accused of being merely verbal disputes: that they are concerned only with language and not with facts. Some think that if this accusation is correct, philosophers should give up doing ontology. However, whether the accusation is correct and whether it is so serious depends on what is meant by verbal dispute. Eli Hirsch in particular has argued that ontological disputes are merely verbal in one specific sense. In this paper, I first argue that his accusation fails to show that ontological disputes are not substantive. Even if we admit that ontological disputes are verbal in Hirsch's sense, they may still be substantive in a variety of other senses. Second, I argue that even though ontological disputes are substantive, the reason for this will not support stronger claims about the nature and role of ontological disputes. / Master of Arts

La thèse examine, à partir d’une relecture de Peirce et de certaines de ses interprétations des philosophes et des problèmes antiques, les arguments qui peuvent permettre à une conception pragmatiste des croyances et de la signification de parer aux accusations de conduire au relativisme. Ces arguments résident dans la façon dont ces conceptions s’articulent entre elles, et acceptent une forme de réalisme / This thesis examines arguments taken from Peirce’s reading in Ancient philosophy, which could be used to block accusations of relativism being latent in a pragmatist conception of belief and concepts. The argument lies in the articulation of the two conceptions and their compatibility with a realist view

This dissertation is centered around a set of apparently conflicting intuitions that we may have about mathematics. On the one hand, we are inclined to believe that the theorems of mathematics are true. Since many of these theorems are existence assertions, it seems that if we accept them as true, we also commit ourselves to the existence of mathematical objects. On the other hand, mathematical objects are usually thought of as abstract objects that are non-spatiotemporal and causally inert. This makes it difficult to understand how we can have knowledge of them and how they can have any relevance for our mathematical theories. I begin by characterizing a realist position in the philosophy of mathematics and discussing two of the most influential arguments for that kind of view. Next, after highlighting some of the difficulties that realism faces, I look at a few alternative approaches that attempt to account for our mathematical practice without making the assumption that there exist abstract mathematical entities. More specifically, I examine the fictionalist views developed by Hartry Field, Mark Balaguer, and Stephen Yablo, respectively. A common feature of these views is that they accept that mathematics interpreted at face value is committed to the existence of abstract objects. In order to avoid this commitment, they claim that mathematics, when taken at face value, is false. I argue that the fictionalist idea of mathematics as consisting of falsehoods is counter-intuitive and that we should aim for an account that can accommodate both the intuition that mathematics is true and the intuition that the causal inertness of abstract mathematical objects makes them irrelevant to mathematical practice and mathematical knowledge. The solution that I propose is based on Rudolf Carnap's distinction between an internal and an external perspective on existence. I argue that the most reasonable interpretation of the notions of mathematical truth and existence is that they are internal to mathematics and, hence, that mathematical truth cannot be used to draw the conclusion that mathematical objects exist in an external/ontological sense.