Mary Leng - 'Ought the Mathematical Fictionalist be a Moral Fictionalist Too?'

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Mary Leng

In the next edition of the Royal Institute of Philosophy Stapledon Colloquium, we are delighted to welcome Mary Leng from the University of York.

Abstract

Ought the Mathematical Fictionalist be a Moral Fictionalist Too?

According to mathematical fictionalism, it is acceptable for scientists to speak as if there are mathematical objects in doing science even if they do not believe in such things, since the purpose of speaking as if there are numbers is one that can be achieved whether or not numbers exist. Moral fictionalists similarly hold that it is acceptable to engage in moral discourse even though they do not think that moral judgements are true, because there is some advantage to moral discourse that remains even if the thoughts one expresses in moral terms are not literally true.

In comparing moral and mathematical fictionalism, I will ask whether there really is a clear purpose that is met by indulging in moral discourse, which justifies continuing to speak in moral terms. Other issues include whether it makes sense to talk of moral discourse as a fiction (mathematical ‘fictions’ are characterized by axioms, but we do not have such an easy way of characterizing the content of moral ‘fictions’?); and whether the motivation for mathematical fictionalism (suspicion of abstract objects) translates as well as may initially be thought into a motivation for moral anti-realism (suspicion of 'queer' moral properties). I will argue that mathematical fictionalism is in better shape than moral fictionalism, both in terms of its motivation and its defensibility, and that the naturalistic motivations for mathematical fictionalism may better support a reductive form of moral realism than an anti-realist moral fictionalism.

- Mary Leng