Biology is driven by complex but precisely known rules (from molecular dynamics down to quark-gluon interactions). That doesn't mean we know how biology works ,

Biology is driven by complex but precisely known rules (from molecular dynamics down to quark-gluon interactions). That doesn't mean we know how biology works , not even for a single person, because it's complex. Psychology attempts to do something much harder, understand the behavior of entire populations of nervous systems. Both are complex, but in principle not uncomputable. And there's a definition of free will: that actions of humans axiomatically cannot be precomputed.