Free will is absolutely integral to defensive apologetics. There are three main areas where it is integral as a defense. Keep in mind, when I say that free will is integral, I do not mean that all of Christianity hinges on the truth of free will. I do mean that for addressing objections, the plausibility of free will seems rather essential. Since it is just a defense, one does not have to prove the response as absolutely true. Only that it is possibly true. For example, if someone says to me that a loving God is incompatible with the existence of moral evil in the world, all I have to say is that free will could be the case. If there is even one possible way for a loving God and moral evil to exist at the same, then the logical problem goes away.
By a free act I mean an act which is the effect of a personal or agent cause with two stipulations. For the agent to be free, the effects it chooses to bring about must 1) not be the deterministic and 2) must not be randomly selected. If my choice to type this was the result of a random neuron firing, which could have fired one way instead of another, it is not free. Even though it is indeterminate, I am still at the mercy of the random neuron firing, and it isn't really me that is causing my actions. Same with determinism. If all of my "choices" are simply the sum of my circumstances, biology and upbringing, my actions don't really originate with me, they originate with things outside of me, which "made me do it." So true freedom is an effect brought about by an agent cause that is not deterministic nor random.
Free will is important to three areas of defense: the traditional problem of evil, the problem of hell, and the problem of miracles. I will briefly surmise how free will helps solve each of these problems. I will not provide an exhaustive solution, just a brief summary of how it helps.
Problem of Evil
The traditional problem of evil states that there is an inconsistency between an all-loving and all powerful God with the existence of suffering in the world. There are two causes of suffering: moral evil and natural evil. In order for humans to have significant freedom and responsibility for one another, they must have the real option of doing harm to another. To take away this option is to rob humans of freedom, and thus the ability to have real love. So even if free will is even possible, it makes sense of why there is moral evil in the world. The same applies to natural evil. If everything was perfect, there would be nothing to sacrifice when loving someone, and thus no significant freedom. So, if free will is even possible, it makes sense of natural evil in the world.
Free will also makes sense of the problem of hell. This is another kind of problem of evil and suffering, but instead related to salvation. The fact that some people choose to resist God and go to hell is also attributable to free will. Now this is a much more complicated issue that can't just be solved using the free will "catch all." However, without free will, no defense of the Christian doctrine of hell could ever be made. We would wonder why an all loving, all powerful, and all just God could let some people go to hell. Free will gets us started dealing with this issue.
Free will also makes sense of David Hume's critique of miracles. According to Hume, we know that testimony of people reporting an event sometimes gets distorted through lying, embellishment, or insanity. However, we know by the laws of nature that a man will never rise from the dead. This would work, except for one crucial problem. As resurrection apologist Michael Licona points out, probabilities of this nature only apply when "intentionality is not present." For example, imagine that my friend leaves his house and leaves a pile of books under the table. Let's say he comes back and see the books on top of the table. Let's say that he tells me that he believes that his books just spontaneously relocated from the floor to the table when he was gone. Hume is right. It is more likely that he is lying, going insane, or just mistaken, than it is that the books just relocated themselves on top of the table. But should I disbelieve that the books were relocated? Hardly. His wife, a free agent cause, probably put the books on the table for him. Once we involve interfering free agents, we can no longer assign a low probability to the relocation of the books to the top of the table. This shows how free will helps even with Hume's problem of miracles.
Even though free will only has to be plausibly or possibly true, it is still good to have some reasons why we believe it is plausibly true in the first place. Here are some:
- Free will accounts for moral responsibility. So all who believe in moral responsibility can only make sense of it through free will.
- We experience ourselves as free agents. We experience our friends as free agents.
- We take time to deliberate over decisions. If we were just emotional robots, decisions would be very fast cause-effect relationships that would weigh our greatest desire and immediately choose that every time.
- We have the capacity to step outside ourselves and observe our own actions as a third party, and make decisions accordingly. We have the capacity for reflection on our actions.
- Christian theology, as a system, generally believes in free will before any of the above logical problems were introduced. This doesn't prove free will, but shows that its not an idea that Christian apologists just made up to save their beliefs. It was already part of Christianity long before we needed to use it as defense.
So this is why the plausibility of free will is essential for defensive apologetics.