Today’s colloquium paper is “An Empirical Argument for Substance Dualism” by Perry Hendricks. Hendricks is a graduate student in philosophy at Trinity Western University in British Columbia, where he also received his BA. His interests include philosophy of mind, philosophy of religion, and epistemology.
An Empirical Argument for Substance Dualism
A common problem with arguments for dualism is that they rely on modal premises that are only supported by dubious intuitions. This results in the arguments having a narrow scope—only those who already hold the needed intuitions will find them to be convincing. In this paper, I try to remedy this situation by constructing a new modal argument whose key premise is empirically supported. I begin by formulating the physicalist thesis and make clear its commitments. Next I explicate the notions of reduction and substance. After this, I argue that Twin Earth—a physical duplicate of Earth (including its history and its inhabitants) is possible and that this possibility is empirically supported. I finish by showing that the possibility of Twin Earth entails that selves cannot be reduced and are not supervenient, and this entails that they are non-physical. Further, since selves are substances, it follows that substance dualism is true.
It is not uncommon to hear the argument that if there is an afterlife, then dualism must be true. However, dualism is false, and hence there is not an afterlife. It is also not uncommon to hear the argument that if dualism is true, then the probability of theism rises. I find neither of these theses compelling—I think that physicalism is compatible with an afterlife and that dualism does not raise the probability of theism—but if my argument is correct, it will provide a way to circumvent the first argument while providing support for the crucial premise of the second (i.e. that dualism is true). However, my argument will bring out a new challenge for theism: if the argument that I defend here is successful, then it follows that God acted arbitrarily in actualizing me over another self (or person). This is because multiple selves could have served the causal role that I do. But then why pick me over someone else? What could possibly ground this choice?
In its barest form, my argument is that physicalism entails that everything that exists is at least minimally supervenient, but selves are not minimally supervenient. Hence physicalism is false. Further, since selves are not minimally supervenient, it follows that they are non-physical. To show that selves are not minimally supervenient, I argue that they cannot be functionally reduced because it is possible for multiple selves to play the same causal role in the world.
One objection that I have pondering recently is that Twin Perry and I do not have identical causal roles because of our differing spatial locations. That is, Twin Perry’s causal role is (slightly) different than mine because he is causally related to Earth in a way that I am not, and I am causally related to Twin Earth in a way that he is not. While I’m not convinced that this difficulty is insurmountable (it is not clear to me that these differences are relevant given my definition of the self), we could tweak the argument to get around this objection as follows. First, note that Twin Earth and Twin Perry are possible. Second, note that this entails that Twin Perry can cause the same actions as I do—Twin Perry and I have overlapping causal powers. Lastly, note that this entails that my causal role does not point only to me, for Twin Perry could cause the same actions—play the same causal role—as I do. Hence Twin Perry and I may be inverted, and the objection mentioned above is rendered irrelevant.
The complete paper is here. Discussion welcome below!