Ned Hall has a paper in a recent _Philosophical Studies_ where he defends a new account of causation. The crucial idea is that we have to distinguish between default and deviant states for certain events/objects. Applied to simple cases like neuron diagrams, the default state of a neuron is to not fire. The theory gets a few complicated cases right, but it seems to not get some even more complicated right. I’ll state (hopefully not too badly) the theory, then offer a counterexample to it. There’s a little bit of interpretation here, because Hall never quite states the theory like this, so I might be horribly misinterpreting something.

C is a cause of E iff there are some events K such that

* each event in K consists of some entity being in a deviant, rather than a default, state
* had every event in K not happened, E would still have happened
* had every event in K not happened, every event in the causal network of which C and E are parts either would have happened in the same way, or would have reverted to its default state
* had every event in K not happened, E would have been counterfactually dependent on C

Here is a kind of counterexample to it. First the diagram, then the description.

* A sets off a chain of events that, if unchecked, will result in E.
* B initiates a threat to E.
* C causes the threat to be cancelled early.
* C also initiates a chain that, if left unchecked, will cancel the threat late.
* D pre-empts this second chain, and will cancel the threat late if it is still present.

C causes E by defusing a threat to it, but it fails Hall’s test. E isn’t counterfactually dependent on C. If D hadn’t happened, E would have been counterfactually dependent on C. But if D hadn’t happened, an event that is actually at default, the one labelled G on the diagram, would have been in a deviant state. So there is no set K as required above, and C is not a cause of E. But this is wrong, since C is what defuses the threat to E.

I think there are also cases where Hall’s theory mistakenly classifies a non-cause as a cause, but those cases are more contentious and I’ll leave them for another post.