Abstract

Belief in substance dualism, the idea that mind and matter are two different kinds of substances, has been found to be a strong predictor of belief in free will. Why? Here, we test whether believing that mind and matter are different kinds of substance correlates with differences in how people think of free will and/or differences in how people interpret the scenarios used to test their conceptions. We provided participants (N = 515) with two hypothetical scenarios where the world was presented either as deterministic or not and asked them whether they thought that a given decision could be free in that world. Incompatibilist free will requires that determinism, the idea that at any instant only one possible future can follow from the state of the world, is false. Compatibilists hold that free will is possible even if determinism is true. In this study, we investigate if substance dualists are more compatibilist. We find that they are not, and that both dualists and physicalists agree that free will is incompatible with determinism. In addition, we show that dualists and physicalists are equally likely to commit bypassing, i.e., to misinterpret determinism as excluding mental causation. We also show that dualists have a stronger tendency to commit intrusion, i.e., to misinterpret determinism by importing indeterministic metaphysics into their interpretation of deterministic descriptions.