Someone on yahoo!answers indicated recently that he is preparing to take part in some sort of debate of fatalism versus free will. He wants to take the "free will side" and he wants to know what argument he has to be most prepared to meet and how he might meet it.
I'm happy that inquiring minds want to know. Here's how I responded.
Let us conceive of "free will" in "incompatibilist" fashion. The basic idea is that the necessity of my actions is logically incompatible with responsibility for credit or blame --- if I robbed the bank from causes that were already implicit a second after the Big Bang, then I could not have done otherwise and am not responsible, in an intuitively powerful sense, for robbing the bank. So, we WANT to believe in free will (indeterminism) because it will make sense out of what we're going to do anyway -- punish bank robbers.
That isn't yet an argument in its favor. But you can create one readily enough from the materials of modern science. Fractal geometry, the butterfly effect, quantum mechanics -- science tells us that indeterminism IS part of the way the world works, so we are not fated..
That's the argument. Now the counter argument. Fatalists will say, "Randomness is just as external and unhelpful from the point of view of personal responsibility as is determinism. Determinism says I robbed a bank because of something true a billion years ago. Your indeterminism says that I robbed a bank because of, what? some uncaused event at the microcosmic level that happened the day I robbed the bank. In no sense could 'I', this macrocosmic person, have prevented either! So free will in the sense you have in mind is doomed either way."
Now, you want THAT counter-argument to fail, right? So here is a rebuttal. In the intuitive sense, I am responsible for an action, I took it freely, if (a) the action resulted from one or more enduring character traits of mine and (b) there was something non-deterministic in the development of those traits. There is no scientific reason to exclude either possibility.