If physicalism is true then:
- The term “my will” refers to physical event B
- Physical event B is causally responsible for physical event C
- Physical event B is causally determined by physical event A
- Therefore, physical event B is causally responsible for physical event C even though it is causally determined by physical event A
- Therefore, my will is causally responsible for physical event C even though it is causally determined by physical event A
- “I have free will” means “my will is causally responsible for physical event C”.
- Therefore, I have free will even though it is causally determined by physical event A
Note that (5) says nothing about free will. It is simply a consequence of (1), (2), and (3). It is true even if (7) is false. But if (5) is true and (7) is false then (6) must be false.