Free Will and Volition
The debate between Free Will and Determinism has been raging forever. It's one of the trickier issues, and there's little agreement on terms. You'll even find arguments about it on Objectivist forums, although the official Objectivist position sides with Free Will. Let me do a little introduction to the topic.
In the most general sense, Free Will is the theory that you have control over your choices. If you decide between doing task A and task B, it's really you that's making the choice, just as it seems to be. Determinism, on the other hand, says that you don't really have a choice at all. It maintains that choice is an illusion, and that your actions are really out of your control.
This topic is important because morality rests on the idea of Free Will. If you don't actually have a choice, then how can anyone blame you or praise you for your choices? Morality is a tool for making choices, and if you have no choice, morality has no meaning.
One reason this is such a hotly contested issue is that the terms are used to describe wildly different concepts. For instance, some people claim that our choices are not determined because our brains are physical, and at the quantum level it's believed (by some) that things only happen by probabilities. Leaving aside the Objectivist's usual complaint about such theories violating the Law of Identity, that's still a terrible defense of Free Will, since it's really just determinism. It still accepts that our choices are controlled by physical laws, but claims the physical laws are random. So what? It just says we're controlled by a random factor, not a deterministic one. This is the kind of confusion that makes the whole discussion seem pointless.
It should be obvious to anyone who can introspect at all that they are making choices. They make them all the time. What's the problem with that? The biggest problem that's difficult for people to resolve is how this ability to choose can exist along side of the Law of Identity. If our minds have identity, isn't our choices controlled by that identity? If our minds are a function of our physical brains, and the brains obey the Laws of Physics, can we really say we're making choices? After all, we had to make the choices we made because of who we are.
I can't possibly answer every question on this topic, since there are so many different views on what each position stands for. I want to just say a few things. First, just because our minds have identity doesn't mean we don't have the ability to choose. The problem here is a strange view of the word choice. It's as if they've defined it to be impossible, since nothing could result in choice. If it were within our control, and our mind had identity, they say it's determined by that identity. If our mind doesn't have identity, there's equally no choice. This should make us discard that view of choice, since it's incoherent.
Determinism amounts to the position that even though we think we're aware of our own minds, it's all just an illusion. One view is that our brains function deterministically based on chemistry and physics, and our consciousness is not real. Essentially, we're imagining our own minds. The assumption here is that because our brains our physical, consciousness must not be real. They can't reconcile the mental world with the physical world, and so they abandon one. So this view of determinism would mean that our thinking is like a TV show, where we are really just passively displayed the illusion of thinking, but we're tricked into believing it's real.
One Objectivist argument against determinism is that it invalidates all knowledge. If you don't really have any choices, then you can't choose between what's correct and what's incorrect. If your mind is just an illusion, then you aren't really grasping (an action) reality. You just think you are. If choices aren't real, then choosing to believe one thing vs. another is not real. Determinism is incompatible with knowledge.
So the Objectivist position is that Free Will is essential correct. Not only that, but our conscious mind is compatible with a physical body. And both are compatible with the Law of Identity. We recognize that our actions can't be evaluated as if they were just random chemical or physical reactions. It's our consciousness that allows us to make sense of the world, and is the key to understanding our behavior. You can't look at men flying to the moon in enormously complex systems and attribute it to mere chemical reactions. Only our consciousness explains it. It is real, and our choices are real. The word choice then doesn't mean being able to go against our identity. It means simply that our minds can weigh the options and come to whatever decision they want to.
I'll have more to add shortly on the exact nature of Free Will. This should give you some info for chewing.