I have learned at least one very valuable thing from Hume: there is no real metaphysical problem in dualist mind-body causation or in temporally backwards causation.
This is a surprising thing to take from Hume, given that Hume does find dualist mind-body causation troublesome and his account of causation makes temporally backwards causation incoherent. But here is my line of reasoning.
We learn from the Inquiry that what intuitively seem the least problematic cases of causation, namely kinematic interaction between solid objects in contact with each other, are as mysterious as cases of causation that we might intuitively find more surprising, like action at a distance. Leibniz thought there was something deeply odd about gravitational action at a distance--it was as if there was a "mutual love, as if matter had senses"[note 1]. But on Hume's analysis, the puzzlement by someone like Leibniz about action at a distance and the lack of puzzlement about mechanistic interaction is simply due to our being overly familiar with mechanistic interaction. However, if we engage in some mental estrangement from the mechanistic interaction, we realize it is just as mysterious as action at a distance.
Likewise, I think mind-body causation and backwards causation are strange, but they are no more mysterious than mechanistic interaction. Since we should not reject mechanistic interaction (unlike Hume, I am willing to take it at face value), neither should we reject the possibilities of the former.
Granted, puzzlement at mind-body causation or backwards causation is not the only argument against these. But it is psychologically the most powerful. The only other form of argument against these is something like this: "On account A of causation, mind-body causation or backwards causation is impossible. Account A is true. Hence, mind-body causation or backwards causation is impossible." But we learn from Hume's valiant failed attempt at a regularity account of causation just how hard it is to come up with an account of causation. In fact, I think all accounts of causation that do not simply take causation to be primitive fail. And accounts of causation that do take causation to be primitive have no special difficulty about mind-body causation or backwards causation.