I'd really like it if someone could explain to me what Aaronson is saying here:

I've often heard the argument which says that not only is there no free will, but the very concept of free will is incoherent. Why? Because either our actions are determined by something, or else they're not determined by anything, in which case they're random. In neither case can we ascribe them to "free will."

For me, the glaring fallacy in the argument lies in the implication Not Determined ⇒ Random. If that was correct, then we couldn't have complexity classes like NP---we could only have BPP. The word "random" means something specific: it means you have a probability distribution over the possible choices. In computer science, we're able to talk perfectly coherently about things that are non-deterministic, but not random.

Look, in computer science we have many different sources of non-determinism. Arguably the most basic source is that we have some algorithm, and we don't know in advance what input it's going to get. If it were always determined in advance what input it was going to get, then we'd just hardwire the answer. Even talking about algorithms in the first place, we've sort of inherently assumed the idea that there's some agent that can freely choose what input to give the algorithm.

-PHYS 771 Lecture