Hi Jonathan! I’m so sorry for the delay in replying. Thank you so much for your comments. I do hope that others will join in the conversation. Let me see what I can do.
You wrote: But I don’t grasp why this is ‘a non-determinist sublation’ (p. 8) or why this is really anything new.
Let’s start with the second thought “What is new about this?” And let’s begin by thinking about it very literally. Not “What’s ultimately new?” but “What’s new, manifestly?” To do so, we can compare what is being proposed to what is already there. In place of a passivist, event-causal account of causation, we’ve got a claim to the effect that causation is what we call the display (or, if you prefer more restrictive, the successful display, relative to a posited outcome) of a thing (“thing”)’s real powers-to-phi. What is “old” – or already there – that is similar to this most basic claim? Well, agent causation, as construed by those who endorse (a) productive, (b) substance-causation, albeit only in the case of agents. Reid is a classical model of this (though he rejects event-causation period, as amounting to substance-casuation where the agent is God).
So, then, the literal version of the question is: “What is different, for the purposes of the free-will debate, between a comprehensive powers-based account of free will and an agency-only powers-based account?” I addressed that fairly narrow question directly in the final section of the paper. On the one hand, with respect only to agents, probably nothing. The upshot is still productive, agent-causal libertarianism. On the other hand, that position – viz., agent-causal libertarianism – is easier to defend (apart from any other advantages to the powers-based ontology relative to a bifurcated passivist/dynamist ontology in which substances that are agents get special pleading) when the background ontology is powers-based, in part for reasons that get us to the less literal version of your question.
This is just the beginning of the reply, but I have to go this minute. I’ll try to finish up later today!