@ora - the only reason we can't predict the whether perfectly is because there are other factors at play that we don't yet see or understand. We don't have all the information therefore our predicitons become less reliable the farther out we get. also, predicting a decision at that moment is different than predicting a decision six months in the future to our limited capabilities. Yes, this applies to the weather as well. Six months down the road, a freak accident may occur that totally alters what our decision would be then versus what we think it would be now. That is the unpredictability due to lack of knowledge. With access to truly 100% of the information, we could predict a person's decisions in the moment as well as the weather, and with 100% of the information involving other's in that persons life and events that we predict to happen (acts of nature, apparently random drunk drivers we could predict because we had 100% of the information from them as well) we can predict off into the futre. But, just as with weather, we can't foresee everything with our limited capabilities, therefore we can't predict everything with 100% accuracy.

You realize that cosmic radiation has an effect on weather, right? Likewise, a drunk driver killing someone's loved one would affect their decisions as well. We only fail in our predicitons because we don't have 100% of the information.

Let me put it in a simpler manner. If I knew everything about a coin toss (side facing up when the coin was tossed, current humidity, temperature, air density, friction of the coin's surface, force applied, exact position on the coin the thumb flick was applied to, upward momentum of the hand as a whole, elasticity of the coin's material and the material it was landing on, etc.) then I could accurately predict every single coin toss. But I don't have that info so it's just a guess. And even if I had it, it would have to be precise. Not "good enough for government work", but very precise.

The same applies to all predictive activity. Predictions are only as precise as the information used. don't have all the factors? Your predicitons fail the fartehr off they reside. Don't have preciswe enough numbers for the factors? Your predicitons have less and less chance of being correct even in the short term.

So to the avergae person, you won't convince them they don't have free will. But to someone who can understand the requirements of accuracy and completeness for accuracy in predictiveness, you can.