Belief is irrelevant. Acting as if you are free is the best strategy in an uncertain universe.
Can you be certain, as in perfectly certain, of anything? No; Descartes pointed out a long time ago all you can ever get is 'reasonable' certainty. Your sense can be (and often are) faulty, as can your reason. No matter how evidence you can find, you can not know anything with absolute certainty; there's wiggle room for doubt.
|Act as if Free||Win||Lose|
|Don't as if Free||Lose||Lose|
Here's the problem; you have it, or you don't.
If you don't, then you cannot, ever, do anything wrong, or have any false beliefs. You have no responsibility. 'You' don't exist. A rigid spacetime exists, and if an entity made that, it's responsible, assuming IT has free will!In that scenario, you cannot make a mistake, because that would imply choice. There would no no downside to behaving as if you were free, or thinking you were, because there would never, ever have been an alternative to that 'delusion'.
But what if free will exists?
If it exists, it's easy to be wrong, about that, about everything.So you might as well act as if you are free, becuase, despite all the evidence to the contrary, you might be, and you will squander this one opportunity to be if you do not.