Some argue that intuitive judgments about mathematical statements lead us to believe in Mathematical Platonism. But the mathematical objects of platonistic theories are supposed to be non-spatiotemporal and detached from the world; more precisely, they are acausal. This is problematic because if mathematical objects are detached from the world, then it would seem that they make no difference to the world. The world would be the way it is even if there were no mathematical objects. Moreover, peop…
Read moreSome argue that intuitive judgments about mathematical statements lead us to believe in Mathematical Platonism. But the mathematical objects of platonistic theories are supposed to be non-spatiotemporal and detached from the world; more precisely, they are acausal. This is problematic because if mathematical objects are detached from the world, then it would seem that they make no difference to the world. The world would be the way it is even if there were no mathematical objects. Moreover, people like Benacerraf (1973) argue that given a causal theory of knowledge, and given its acausal nature, we could never know about mathematical objects and therefore should not postulate them. Elsewhere in the literature, indispensability arguments are made for mathematical objects (e.g., Baker, 2009). Our best scientific theories seem to rely on explanations that quantify about mathematical objects, so we should believe in them just as we believe in the unobservable objects of science. We can then say that we know mathematical objects exist by inference to the best explanation based on our best scientific theories. But that doesn’t tell us what mathematical objects are like, and most importantly, it still doesn’t answer the »makes no difference« argument. We may be forced to believe in them, but that doesn't tell us whether or not they actually do anything. I'd like to discuss one way that mathematical objects might do something. I think there is a useful and informative way we can talk about mathematical objects as causal. I do this by discussing a case of mathematical constraint as proposed by Marc Lange (2017). I will elaborate on the notion of mathematical constraint and talk about the constraint relation in general. I then discuss structural equation models and how they can be used to represent causal relationships. This fits particularly well with the interventionist view of causality that I will describe, and how it can be used as a test to determine which relationships are causal. I think that mathematical constraint passes this test. Using this framework, I will discuss a specific structural equation model that represents a constraint relationship. This specific constraint relationship is also clearly causal. I think that the structure of this relation naturally maps on to the structure of an archetypal example of a mathematical constraint. Not only do they share a common structure, but both relations behave in the same way in interventionist treatments. This should give us reason to say that mathematical constraint is causal. For those interested in the epistemology of mathematics, this may provide a workaround to Benacerraf-type objections; it would be puzzling how we know about acausal mathematical objects, but since mathematical objects are causal, we can explain our knowledge. For those who sympathize with or are concerned about the »makes no difference« argument, we again have an answer: mathematical objects are causal, so it would make a difference to the world if they did not exist.