I am struggling to understand what Schopenhauer could mean by his definition of free will. Unfortunately, he doesn't give examples or put the way he uses the term in context, so I suspect Wittgenstein would have some difficulty accepting that it is truly meaningful.
I have recently been watching the excellent videos on the philosophy faculty website:
In part 5 Peter Millican touches on free will a few times, in particular in relation to the mind / body dualism debate. He makes a very interesting analogy. If we try and think about ourselves in terms of a computer, we have hardware (which explains our physical actions in terms of cause and effect) which extends to the physical and chemical constituents of our brains. We also we have software, which is analogous to our minds.
We cannot fully explain our minds by just talking about physical properties or causation. Using this analogy I would maintain that our minds are programmed in such a way that we are free to make moral choices and decisions. I can't explain why this is the case, but I certainly do believe that it is the case.
I think looking at the way we use the words "free will" helps, but Schopenhauer seems to be looking for a metaphysical explanation of what free will is, whereas explaining the terms by how they are used seems to be edging towards an epistemological explanation.
Is it possible to answer metaphysical questions by looking at the philosophy of language?