Chapter 5: The problem of free will and determinism

Free will supplement: Libertarianism and dualism

Matthew Van Cleave

It sometimes happens in philosophy that a position one takes on one issue has implications for another issue.[1] A good example of this is the relationship between the “libertarian” position in the free will debate and a position called “dualism” in the mind/body problem debate (see the chapter on the mind body problem in this textbook). Recall that the problem of free will concerns how there can be any room for free will in a deterministic physical world. If the physical world is deterministic and if the mind is just the brain, which is itself a physical system, then it seems that there is no way to escape the conclusion that all of our actions, which are routed through our minds, are themselves deterministic consequences of what precede them. Thus, since the libertarian claims that there is free will and that therefore determinism is false, she needs some account of how our minds can escape the deterministic realm of the physical world.

Modern philosophers such as Rene Descartes and Immanuel Kant were well aware of this problem and this is in part what led them to subscribe to dualism.[2] Dualism holds that the mind is not a physical thing but an immaterial thing. This means that for the dualist the mind is not the same thing as the brain. Rather, the mind exists in a different realm from the realm of physics. If the mind is immaterial then this means it is not subject to the deterministic laws of the physical world and this, in turn, leaves open the possibility for an incompatibilist (libertarian) account of free will to be true. If the causes of our actions do not issue from a physical system like the brain, but instead issue from an immaterial mind, then it is possible for us to say that I could have acted differently, even if all the same conditions were in place. Dualism insulates the mind from the physical realm and thus makes possible an incompatibilist, libertarian account of free will.

Of course, just because dualism supports the libertarian account of free will doesn’t mean that dualism is true. As a theory, dualism stands or falls on its own merit, based on how satisfactory its answer to the mind body problem is. The point I am making here is that it is an attraction of a theory that it can help us resolve puzzles in other philosophical areas. That a theory about x can also help us to better understand some other thing y should be a factor in our overall assessment of philosophical theories. This is no less true in philosophy than it is in science.

Other philosophers question whether dualism really provides the kind of account a libertarian owes us. It seems to these philosophers that invoking dualism in order to explain how human actions are insulated from determinism is just trading in one mystery for another. The most central objection to dualism is the interaction problem: how can an immaterial, nonphysical mind interact with (for example, cause) things in the physical world? We really have no idea how this can occur and this has been a problem for dualism ever since Elisabeth, princess of Bohemia raised it in correspondence with Descartes.


  1. Thank you to Christopher Schneck for suggesting that I make the connection between libertarian accounts of free will and dualism explicit.
  2. It is not the only reason they were attracted to dualism, however. Within a Judeo-Christian worldview, the idea that humans have an immaterial soul was also an influence on modern philosophers like Descartes and Kant. Indeed, until the second half of the 20th century, dualism was the most commonly held position on the mind body problem among philosophers.

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Introduction to Philosophy by Matthew Van Cleave is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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