While I appreciate phunwheel's post, I am going to have to respectfully disagree with his assertions. The way a man acts or reacts to a situation is entirely dependent upon his brain functions. This is indisputable scientific fact. The chemistry in the brain is what determines our thoughts, our emotions, and most importantly determines my body's movements.

Furthermore, the brain is constantly being inundated with different chemicals which trigger neurons telling us to breath, sending hunger pangs, or signs of danger. These chemicals can even function to make us feel love, and even spirituality, as researchers recently found that deeply meditative monks and those in deep prayer actually have the receptor which orients us in space blocked, thus leading to a feeling of "infiniteness" or out of body experiences.

If each receptor in the brain is what controls our thoughts, feelings and actions, and these receptors are triggered or blocked due to some previous stimuli, then how is it that humanity has free will? He is a slave to his own computational mind. Indeed, one could argue that the stimuli themselves may be controlled in such a way as to produce free will. But those stimuli are acting under the same natural laws and are produced by some other brain process or physical reaction somewhere, which itself was due to another stimuli which triggered those thoughts/actions before it. Onward, and onward, back to infinity.

It is argued that the fact that there are infinite different stimuli that you may be exposed to, and that at any time there are an infinite number of things which may stimulate you, tears down the idea of pre-determinism. However, this argument breaks down because our brain is not an infinitely capable computing machine. Our senses are limited. We cannot process an infinite amount of information at once, and we cannot sense everything, both physical and emotional, about any situation. Our brains are limited by a specific number of receptors, a specific speed at which it can compute, and a limited number of chemicals, each of which will trigger a predictable response in the brain. Suicide does not prove non-determinism. Rather, it shows that someone's brain chemicals have triggered a response in them that they no longer want to live. Their minds have observed some stimuli, and upon seeing the information presented, their brain triggers a number of neurons in the brain to make the person feel the need to kill himself, this decision then triggers the chemicals which produce the action of suicide itself to take place in the person. As sad as it is, suicide is no more a choice than death itself. It is simply a reaction to certain stimuli that forces the person to act in such a way that causes bodily harm, and we cannot tacitly accept this as choice.