There's a difference between free will as a philosophical debate compared to a question of biology/chemistry/physics. It matters as a point of principle to the

There's a difference between free will as a philosophical debate compared to a question of biology/chemistry/physics. It matters as a point of principle to the physicists who are asking questions about whether true randomness exists - if the physical world can be influenced by something outside of the natural forces they know about, they want to measure that force, even if measurement and computing equipment to model the universe down to the Planck scale cannot exist. Where it really matters is when you get to computer simulations: Without access to a source of non-determinism, an AI can hardly be said to have free will. Give the same pattern of bytes running on the same instruction set the same inputs, and it will deterministically generate the same outputs.