The issue of free-will–and here I mean free-will in the broadly libertarian sense–is fascinating, but as interesting as that issue, in and of itself, is, free-will is also interesting in that it is an issue which can give us a very simple and intuitive argument for the existence of god, for consider the following layman’s chain of reasoning:
1. All my experience tells me that I have free-will and all of society is build on that belief, and so I am rational to believe that I do have free-will until and unless given good reason to believe otherwise;
2. Something like free-will can only come from something that has and/or can create free-will;
3. The only thing that I know of that has free-will are persons (minds), and so the best explanation is that my free-will comes from a person (a mind), but the chain of persons cannot go on infinitely, and therefore there must be an uncaused and first free-willed person who is the cause of all the other free-will in other persons, and such a person deserves the label of a god…
…and when put into more philosophically rigorous terms, the argument might go like this:
a. I have a properly basic belief that I have libertarian free-will, and therefore, not only am I rational to believe that I have it, but, because it is a properly basic belief, the burden of proof is actually on the person denying this belief to demonstrate his case, not on me to prove it, and so I am rational to hold to my belief that I have free-will until and unless a sufficiently warranted defeater is brought against this belief;
b. There are no sufficient defeaters to my belief that I have libertarian free-will;
c. Given the Principle of Proportionate Causality (which states that an effect must, in some way, be entirely contained in its cause), I thus note that whatever caused me to have free-will must somehow have the causal resources / ability to create free-will to exist in something else.
d. Not only are there no known impersonal forces / mechanisms which could cause free-will to exist in something else, but the only things that I know that have free-will are personal (rational) entities like me (essentially, minds).
e. In light of the above, the only presently known causal explanation for my having free-will is that it was caused in me by some other personal (rational) entity which can create free-will, but such a chain of causality cannot go on to infinity, and thus, there must be a first and uncaused personal (rational) entity which exists (or existed) which has the ability to cause free-will and which gave free-will to all other personal (rational) entities that exist and have free-will, and any such uncaused personal and rational entity with free-will that exists (or existed) deserves the label ‘god’, and so, given all this, I am rational to be a theist, not an atheist;
f. Or, alternatively, for a “Inference to the Best Explanation” type approach to this issue, one might, after point (d), simply point out that between atheism (atheistic-naturalism) and theism, atheism simply does not have the ‘explanatory power’ to account for the existence of free-will in persons like theism has (an omni-God could give free-will to others by definition), nor is atheism ‘congruent with the background knowledge’ that only persons have free-will, nor is atheism simple given that it postulates an impersonal “thing or force” which is somehow (miraculously?) able to confer free-will to persons through some unknown mechanism, and so theism is therefore the better explanation of free-will, and thus theism is rational to believe in on the basis of free-will, at least provisionally.