I’ve been thinking about overdetermination a bit recently, as it relates to the mindbody problem.

Traditionally, overdetermination is presented as a sort of third way out of causal exclusion arguments. You don’t say that mental states have no causal powers (I.e epiphenomenalism), and you don’t say that your mental states are the unique cause of any physical goings-on, instead, everything caused by your mental states are caused twice over. Once by your mental state, and once by a physical process, such that both would be sufficient on their own to cause the physical event in question.

I don’t really think overdetermination is an improvement over either other option. I think, actually, it’s probably worse. The main intuition against epiphenomenalism is that our mental states clearly seem to have causal powers. It just seems incredibly obvious that my pain is what causes me to wince and groan. Now, I think that along with this belief comes another belief of mine: that if I wasn’t in pain right now, I wouldn’t be wincing and groaning. This seems to hold even more strongly with cases of intentional action: Not only does it strongly seem to me that my forming of the intention to raise my right arm causes my right arm to rise, I think that if I didn’t form that intention, my right arm would not have risen.

If overdetermination is true, that second belief is false. There was another physical cause sufficient for my right arm to rise which would have made me raise it anyway.

Tack on that this view already has to violate causal closure (unlike epiphenomenalist views) this just seems like the worst of both worlds! You have to deny a strong counterfactual intuition and deny causal closure. On either other option you only have to do one or the other. So I think, if you’re a dualist, you should probably shoot for epiphenomenalism or interactionism, rather than overdetermination.