The notion that free will does not exist.

This is a well thought out and well-constructed argument. As an existentialist, however, I am inclined to disagree. Although it is evident that a choice was made after an action of will, it is by no means clear a priori what that choice will be. I understand your arguments and follow your logic. Your main claim is that if all of the precusors that lead to one choice over another could (even hypothetically) be determined to arrive at the proper conclusion as to what choice will be made, then man truly has no free will. On this, I actually concur. If it is theoretically possible to predict all of our choices a priori, then choice is nothing more than an illusion. But I assert that predicting all acts of will before they take place is not only physically, but also theoretically impossible. As you rightly point out, such impossibility of prediction and indeterminable free will would only be possible by the means of something spontaneous and random. This is precisely where we differ. I believe in this random element that allows for free will. Causality flows only one way. There is a cause and then an effect. Performing an analysis of the act of will after it has occurred changes nothing with regards to determinism. Saying that you know which choice was made after it has occurred does not mean that you would know this choice before it occurred. Such post hoc analyses are known to be fallacies. So now that I have established that I will not use such arguments (that you have pre-empted) as "I appear to choose, and therefore I do," I will get to the heart of the matter. Your claim was "Spontaneity and randomness is absolutely unverifiable, while causality is very much verifiable (and, in fact, is the basis for verifiability)." This is where the problem lies. Randomness IS verifiable. There are tests to determine whether or not a series of numbers is random. Random number generators can be programmed (though these are only truly random when an additional program is added to delete the programs memory of the preceding given values). To this you may claim that random number generating programs are not installed in humans. A series of numbers on a computer, after all, does not show the true randomness of human choice. And so this missing random element that allows for free will should come from another source. For that source, I must turn to the realm of quantum physics. In quantum physics, there are many experiments that are done that have actually verified randomness. The phenomenon that shows this best is that of superposition. Superposition is a state in which a sub-atomic particle is actually in two states at once. Of course these notions in quantum physics contrast greatly with our daily experiences, but they have been verified time and again through experimentation. Now in superposition, the particle can be in two states (such as spin up and spin down) or even travel two different paths (such as go through both slot A and slot B in a double slit experiment). Now what happens with superposition is that after the particle in such a state is observed, it suddenly "chooses" one state over the other. This "choice" is completely and totally random. There is no way to predict which state the particle will choose (even hypothetically). In fact, the laws of quantum physics state that this act of decoherence (decoherence is the act of leaving a state of superposition) can never be predicted. There are many other experiments done such as creating two particles where one will be spin up and one spin down that both start in a state of superposition and then decohere. But this is not a debate on quantum physics, so I will make my point. Man is comprised of various cells which are in turn made up of molecules which are made up of atoms, et cetera. At the most reductionistic breakdown, we are comprised of a large number of quantum particles. Since these quantum particles have been shown time and again to exert truly random behavior, humans do in fact have that random factor that allows for free will. So when you claimed that there must be a random factor for us to have free will, my answer to you is "There is!"