Sorry for the delay - I've been otherwise engaged.

NightWing: if all is caused, there can be no such thing as free-will, an "uncaused effect". That's my argument.

Skeptic: aren't you mixing up predictability with causation? I don't think that Chaos Theory says anything about cause and effect, though it does, I agree, have a lot to say about the unpredictability of complex systems (I'm no expert on CT: shoot me down, do, if I'm wrong). But my argument has got nothing to do with predictability. If there are no uncaused effects then my thoughts, too, are caused, and I can't see why caused = true (when we can see the cause of thoughts, we discount them, eg when the drunkard claims to see pink elephants we don't bother looking for them). Therefore I have to argue that cause-and-effect is not universal, because the converse leads to the reductio ad absurdem:

there are no uncaused effects
therefore I cannot rely on my thoughts being true
therefore I have no reason to suppose that there are no uncaused effects