This entire discussion is based on the assumption that the physical world is predictable in principle.
Ah!
This I understand...and yes, it's generally almost always true...as I understand it, the universe is pretty Newtonian...
But not entirely...and it seems to me that Life is, by definition, adding a little more randomness to what are ordinarily straightforward chemical processes.
You then add sentience and mobility to that life... and you've randomized things some more. A plant can't get up and run away, or decide where to bury it's poop to conceal its' activities...or carve a fertility statue.
Does that constitute free will?
Heck...how are we defining free will again?
Ok, here's a nice concise one found at:
http://dictionary.reference.com/browse/free+will
free will
–noun
1. free and independent choice; voluntary decision: You took on the responsibility of your own free will.
2. Philosophy . the doctrine that the conduct of human beings expresses personal choice and is not simply determined by physical or divine forces.
As much as I seem to do anything and this isn't all an illusion (which I'm willing to entertain), I would say I engage in the first.
The second? hmm...I like to wear men's clothes.
I do not see this being determined by a physical or divine force, but by the fact that the assemblage (yes, I'm not entirely unified, and better yet, my inner sociopath does the driving these days, and he wants an SUV with a giant brush-guard
) known as "I" "like" clothes that are generally designed for people who have a slightly different set of body attributes than my own. This leads to them being ill-fitting in the bum, but the trousers designed to fit my rump are often lacking in toughness and roominess...
and they may have flowers on themuke:
The men's clothing does not seem to be chosen by a physical or divine force. I do, in fact, go pick out my trousers, inasmuch as I "do" anything.
However, if I choose to step off the edge of a 300-foot bridge without a parachute, I subsequently do not have any more choices, I will be becoming very flat shortly. I cannot choose to flap my arms and fly at that point.
So while we have a selection of things we may choose to do, they are limited by physical constraints.
I guess I would argue that we have...the appearance of a limited amount of free will, insomuch as we have anything.