If all events have causes, then nothing can happen spontaneously. A “will” in that world can’t be “free” or disconnected from the causal chain.

If there are events that don’t have causes, either they are random, or we need to introduce an unfalsifiable explanation. In a random world, a “will” is still constrained by rolls of the dice. It does not express itself. It is not “free”.

If we introduce a metaphysical explanation, then it is no longer science, and can properly be discarded as “nonsense” in the context of the project of inquiry into the physical world. In its company we find concepts like souls, ghosts, deities, magic, etc.