The free will and determinism debate has been around for quite some time now and today is still going on with many open ends.This site http://www.thegreatdebate.org.uk/determinismandfreewill.html goes especially into great detail about each side for free will and determinism.
After reading through the many arguments I would have to say that I am leaning towards determinism. If you really think about it, there really isn't anything that is "original". Everything is a factor or a branch off of something else. There just isn't that one original thought, idea, action, etc. In the article, they gave a supposedly example of free will is a spontaneous act. Such as the growth of plants or the impulsive movements of animals. But, you then ask, well why did the plant grow or why did the animal move? Well the plant grew because the seed was dropped there by a bird and there was ample sunshine and water; conditions just worked. Or, the animal moved because it was startled or saw something it liked and moved or maybe they have a muscle disorder that was caused by a disease picked up at the waterhole that was from...etc. You get the point. Everything factor is caused by another factor. Just as the book says, we may think we have free will but I personally think determinism is what truly exists.