Ought the mathematical fictionalist be a moral fictionalist too?

Metallurgy and Materials (GA03)
Arts and Law, Engineering and Physical Sciences, Lectures Talks and Workshops, Research, Students
Wednesday 6th December 2017 (16:00-17:00)
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Mathematics and Philosophy Seminar

The talk (including discussion) will last approximately one hour and will be followed by refreshments. All welcome. 


On the face of it, many of the motivations for mathematical fictionalism would appear to support moral fictionalism too. We find it incredibly useful, perhaps even indispensable, to speak as if there are mathematical objects, and yet the platonist's abstract mathematical objects are rather queer entities, and it is difficult to explain - from a naturalistic perspective - how creatures like us could have knowledge of things like that.  Similarly, it is hard to imagine doing without moral evaluation and our usual talk of moral reasons, but the idea that some facts could function as categorical reasons to act, independent of any individual's motivations, has similarly struck many as queer and epistemologically objectionable. In the mathematical case, the mathematical fictionalist defends her continued use of mathematics by providing an account of (a) what purpose they aim to serve by speaking as if there are mathematical objects, and (b) why it is reasonable to expect our mathematical theories to be successful in serving that purpose if one does not believe in mathematical objects.  Moral fictionalism requires an analogous defence, if it is to be a plausible position.  However, looking at the various accounts moral fictionalists have given of the purpose of moral discourse, it is not at all clear either that it would be reasonable to expect moral discourse to serve those purposes effectively if one did not believe in categorical moral reasons. I suggest, then, that moral fictionalism is in a worse position than mathematical fictionalism in lacking a compelling account of why it is reasonable to continue to speak 'as if' there are moral truths if one does not believe that there really are any.  If mathematics ought, for a coherent overall position, to adopt moral fictionalism too, these failings in moral fictionalism might lead to an instability in the mathematical fictionalist's position. However, I conclude with some reasons to think that, if the motivations for mathematical fictionalism are borne out of a form of Quinean naturalism, then it is plausible that these motivations actually push in the direction of a realist approach to moral discourse, rather than towards moral fictionalism.