I wish for healthy criticism of my argument below and see if it holds true. These are just my own ideas, influenced I guess a bit by Thomistic thought. Please fill free to add your 2c or $100 worth.
If one holds the tenet that a human being is entirely comprised of nothing else but matter, then it holds that matter must be the source to every characteristic found in the human person. This means that all faculties including cognition, thought, reason and will must be brought about by an internal interplay of matter alone. All actions and faculties of a person are brought about by a cause-effect, and if one were to follow each cause/effect to its origin we will arrive at a first-cause or first-mover for every act. Being that our bodies are finite, then it holds that the cause/effect series itself must also be finite. Therefore a first-cause must exist and in order to maintain the atheistic proposition as true, this first mover must exist within the human body. Now taking “will” as our object of interest, I dare ask, where does the ability to choose come from? The source must be matter, but how can atoms bring forth choice? Matter can by no self-intervention dictate the outcome of its state as it is subordinate to the law of nature and has no capacity to free itself from the laws of physics. Hence we have to ascertain that choice is but a randomness of enough complexity as to make us incapable to detect its many variables that have set it forth into existence. And that rather than our wills instigating the act of choice, our consciousness merely becomes aware of the act without its immediate consent and that it then falsely holds the notion that it was the cause to the “choosing”, while all along it is merely our materialistic composition that hold what our actions are to be. I cannot see any other explanation within the realm of atheistic thought than that put forward.
Many questions arise from this; one in particular is accountability of our acts. How can judgement befall on us if we are pre-destined in our actions when faced to specific situations and stimuli? Therefore, one can see that self-governance of the will cannot exist under this proposition; rather will is but a subordinate faculty receptive fully to a pre-determined outcome determined by the materialistic composition of the human person and the external environment that influence it.
Cheers and God bless