PUB - Publikationen an der Universität Bielefeld

Nominalism (the thesis that there are no abstract objects) faces the task of explaining away the ontological commitments of applied mathematical statements. This paper reviews an argument from the philosophy of logic that focuses on this task and which has been used as an objection to certain specific formulations of nominalism. The argument as it is developed in this paper aims to show that nominalism in general does not have the epistemological advantages its defendants claim it has. I distinguish between two strategies that are available to the nominalist: The Evaluation Programme, which tries to preserve the common truth-values of mathematical statements even if there are no mathematical objects, and Fictionalism, which denies that mathematical sentences have significant truth-values. It is argued that the tenability of both strategies depends on the nominalist\textquoteright{}s ability to account for the notion of consequence. This is a problem because the usual meta-logical explications of consequence do themselves quantify over mathematical entities. While nominalists of both varieties may try to appeal to a primitive notion of consequence, or, alternatively, to primitive notions of logical or structural possibilities, such measures are objectionable. Even if we are equipped with a notion of either consequence or possibility that is primitive in the relevant sense, it will not be strong enough to account for the consequence relation required in classical mathematics. These examinations are also useful in assessing the possible counter-intuitive appeal of the argument from the philosophy of logic.