I think you mean to say 'belief' instead of 'knowledge', since most of the time when people decide to do something because they think it's best option they're wrong.
Don't see it as hugely important, but sure, maybe.
But either way, I think it's easy for libertarians to deny both parts of your antecedent and say that the will is implicated in belief and also that beliefs underdetermine decisions. What about people who hold beliefs because those beliefs are comfortable and unpleasant to challenge? Isn't the will implicated there? And what about impulsive decisions?
People holding beliefs because they're comfortable doesn't imply free will in and of itself. You'd need to be clearer about what you mean by 'impulsive decisions' (ie, avoid defining them solely as 'decisions not made by virtue of regarding a proposition as true').
I just had to say that this is really annoying. Like, obviously if I know you're going to do x, then you're going to do x. But this is a point about our concept of knowledge and not about some capacity that you may or may not have. This bit about being "powerless to prevent x" is just so wtf - my knowledge is the dependent variable here, not your behavior. I think language like this is why people get confused on this topic.
The theological version of this is kind of interesting though, what would theists sooner give up if they can't make them compatible: God's omniscience or the only seemingly sensible answer (free will) to the problem of evil?
Due to the bump of this thread, my search for meaning in life, the acidic taste of my orange juice this morning and I'm sure many other reasons of which I'm unaware and cannot control, I'm compelled to make a tl;dr post ITT.
Trying to fathom how free will could exist in some form even though it appears incoherent in a deterministic system, I’ve run across a couple ideas. One states QM in our brains could somehow be a source or trigger for FW, and another is Dan Dennett's idea that FW may have evolved out of deterministic processes in a similar way life evolved from non-living matter. Neither proposes a mechanism, only speculates a framework. I would like to add a thought which could tie these two ideas together a bit, but regrettably still won’t give us anything in the way of an actual mechanism.
Part of the reason QM is interesting in this discussion is that randomness is incoherent according to determinism, so if quantum randomness actually does occur in nature then things apparently can and do break the rules of determinism after all. There is another place in nature we can look to see a breakdown of our understanding of the rules... a black hole.
Proponents of determinism claim determinism holds in every situation from the simplest to the most complex, and that no level of complexity will undermine the causal chain of events, but what if that's incorrect? One property of a black hole is its extremely low entropy, and many believe as we approach and cross the event horizon, causality takes a smoke break. A human brain is among the most organized objects we know of in the universe. What if at some point in our brain’s extremely high organization, an event horizon of sorts is formed past which the rules of causality are bent. Could humans be running around with singularities in our heads (some more supermassive than others) around which the rules of causality bend enough for us to inject some influence into the causal chain, granting us real responsibilty?
Pretty out there, I know. Even so, I doubt I’m the first to think of such a thing. I have no idea if we’ll ever be able to make the incoherent concept of free will coherent, but I have an idea of how rare intelligent life is in this universe (I think we’ve discovered way more black holes so far), so if it exists somewhere I think we’re looking in the right place.