http://www.rationalresponders.com/free_will_why_we_don039t_have_it_and_why_that039s_good_thing

There are philosophers, compatabilists, who hold that determinism and free will are reconcilable, but I don't know they're arguments.

 I'm not sure if this will answer your question or not, but I hold to the belief that "free will" is a nonsensical term, literally devoid of real meaning.  It is the same as "God" or "supernatural" in that sense.  Humans are autonomous, but that's nothing particularly special.  Pretty much all animals are autonomous.  The thing is, we are aware of our autonomy, and it seems really special to us because of that.  I suspect that a lot of theists have succumbed to a rather bizarre flip-around logic.  They can imagine not being autonomous, and that scares them, so they think "free will" is some kind of gift.

Maybe that's why some people think there ought to be free will?  I dunno.  In any case, it's not that we don't have free will.  It's that free will can't be defined coherently.  We might as well say we don't have any invisible colors.  What the hell is an invisible color?  See what I'm getting at?  Of course we don't have any invisible colors because those two words don't make any sense together.  We can't even say what an invisible color would be.

Free will means to exercise your will freely, making your own decision without benefit of an invisible deity jigging your brain cells for you. It's balderdash. Utter crapology - like the parent concept which necessitated its coining.

If you are atheistic you do not exercise free will. You cannot exercise free will. It doesn't make sense.

You do however behave constantly in a manner contingent on the last decision your brain arrived at, whether it was formed consciously or sub-consciously, a product of conditioning in a compliant or reactionary sense, with or without useful deliberation, with or without deliberation at all, or whether it was informed or completely intuitive. In making your decision you exercised neuron activity and bridged synapses in at least one but more likely several areas in your brain which themselves had their activity at that moment influenced by the general physical state of the areas in question, a constantly fluid state easily adjusted in quite drastic ways by externally and internally sourced chemicals all the time. You exercised your brain, but your resultant "decision" was in the process therefore a result of a sequence of such "decisions", few or none of which were registered even sub-consciously but all of which could themselves have been your "decision" had the process stopped there, as it indeed most likely had in the past with sufficient regularity to encourage a repeat of that pattern.

Some of these past patterns are available to you as "memory" but the majority need not be, the resultant apparent randomness and spontanaeity of the outcome allowing you to believe you have behaved with total freedom of choice subject to the data you acknowledge as input but in reality has left you with little choice in the outcome. You do this however several hundred times a second, so the perception of randomness is encouraged by the fact that you only consciously register an outcome of the process very rarely in comparison to the number of times the process occurs.

You do all this, over and over, from birth to death. It is not "free" as it is limited physically by brain function, but it is still capable of huge variations in output, and at least some of that output can be consciously directed to occur, so you can be forgiven for sometimes using the shorthand expression "free will", however inferior it is to the actual description of how you decide how to behave.

Bertrand Russell once explained to an audience of students  that oxymorons often reveal much that is problematic with those who employ them, but rarely with language itself ."But what then if both sides of the oxymoronic phrase are equally non-descriptive of the event they try to describe?", a student asked. To which he answered "Then we just drop the "oxy'".

Of course you've got to remember too that the guys who cobbled together the notion of "free will" were working on a hunch that it all happened in the heart, so that might explain why they were a bit stunted in their terminology.

If you're looking for in-depth discussions on the neuroscience of consciousness, I suggest:

Lawrence Tancredi's "The Neuroscience of Free Will"

Bechara, Burns, and Kelly's "Decision Making and Free Will: A Neuroscience Perspective"

Susan Pockett's "The Concept of Free Will: Philosophy, Neuroscience and The Law"

Or, for lighter reading:

Chris Frith's "On Nailing Free Will"

Economist's "Free To Choose?"

It seems to me the idea is strongly pushed, if not invented, by Christians trying to reconcile the concept of God punishing his creations for actions they are inevitably guaranteed to do because of the way they have been 'designed'.

The entire free will v predestination thing is a very old bit of mental masturbation which is really not worth wasting time on.

First one has to realize that simply because a question can be posed it is necessarilly a legitimate question.

In this matter we have two conjectures as to the nature of our reality. There is no possible test to determine which is correct. There is no way to rerun the past.

Therefore all talk of it is what I have come to call mental masturbation. Thinking on such universal concepts feels good but can never be productive.

 I'm pretty sure that the most coherent definition of what people think they mean when they talk about free will is... let's see... second order awareness.  That is, I am aware that I'm aware of my potential actions.

Let me explain.  To an observer, I am no different in action from a common spider.  If a spider and I are both walking, and we come to a barrier, both of us will either:

1) stand still

2) turn back

3) turn left

4) turn right

5) climb over.

The fact is, neither of us has a choice about making a choice.  Unless we die on the spot, we must perform an action.  Again, to an observer, we are no different.  Both of us are bound by the laws of time and physics.

The difference between a spider and me is that a spider, by all indications, acts without thinking about thinking about its action.  It thinks about its action in some way.  That is, its brain processes data and its body responds dynamically to changes in the brain resulting from the "output" of the processing.  That's what brains do.  However, the spider is not aware that this is what its brain does.

I, on the other hand, know that my brain controls my actions, and I know that I can stop and contemplate my actions.  That is, I can think about thinking about my actions.  This is second order awareness.  It is also what I believe most people mean when they say they have free will.