Your question is ambiguous, because the word "reason" can have several different meanings in the context of the question. By a reason do you mean a teleological one, or do you mean a "cause" which reason can understand, for example.
If you mean reason in a teleological sense, that would imply that everything that happens does so because it was intended by someone (God), and therefore was simply the revelation of a fully scripted play, where "cause and effect" were nothing more than an illusion of the play.
If you mean simply, every event has a cause, you are describing the strict naturalist view which cannot include any teleological aspect at all. Every event can be fully understood in terms of all the events the preceded it as the cause of that event. Nothing else is needed.
This, of course, presents a dilemma. If the world is teleological in nature, cause and effect must be an illusion. But that would negate all scientific knowledge, and, in fact, all knowledge based on observation. It would mean that no prediction of anything in the future could be certain, because nothing could depend on cause and effect, only on whatever was in the script. The sun might not rise tomorrow, and the simplest thing you are sure of, might never happen. Tomorrow, your corn flakes might taste like fish and be poison.
But, if everything is simply a cause-and-effect inevitable chain of events, there is no room for the teleological at all; no room for any purpose, any value, or any meaning. Everything that is would just be because it is, and everything that happened would happen because that is what had to happen given the chain of events that led to it.
Something is wrong with both of these views. It cannot be a script, because we know things are caused. If they were not, we could not hold anyone responsible for anything. If pulling the trigger of a gun was not the cause of its firing, who could be tried for murder with a gun?
But if everything is caused, how can there be any purpose or meaning, and how could we know it, since even our thoughts would only be caused events, with no more validity than a sneeze.
There must be something else. And there is. It is called volition. What is volition?
Well, first of all, that is the question you should have asked. Volition is the faculty that enables the rationally conscious to choose their behavior, which includes both thinking as well as overt acts. Volition means those conscious choices that are neither scripted or caused. It is that aspect of human nature which God gives to every human being that enables them to choose, by whatever means they choose, what they will do.
Volition applies only to that which is possible, that is, what is physically and intellectually possible. A human being cannot choose to do what is physically impossible for him to do, and he cannot choose what is intellectually impossible to do, that is, he cannot choose what he cannot know, or is incapable of understanding.
Volition makes man morally responsible, but moral responsibility only pertains to volition, and therefore, to what it is possible for a man to choose. If any aspect of his life is determined by anything other than volitional choice, such as a "script" or a "cause," that aspect lies outside the province of moral responsibility. No man is morally responsible to make any choice it is impossible for him to make.
So, whatever you decide predestination means, the one thing we know it cannot mean, is that any man is morally responsible for anything that happens in his life because it was predestined (by script or cause), and God does not judge any man for what is impossible for him to choose.
Hank
I don't understand this comment. As I see it (paraphrasing Aristotle) efficient and final causes are not contradictory, they are complementary. For example, if I walk to a cafe for lunch, the efficient cause of my arrival is my feet moving me. But the final cause is my desire for lunch. How does the one negate the other?
Isn't it entirely possible that efficient causes are how God makes things happen, and final causes are why he makes them happen?
By the way, if you follow mainstream Christian theology, God does not have "foreknowledge" of anything. God exists in aeternam, outside of time; time is part of the created order, coextensive with the Universe. God therefore has only knowledge, timeless perfect awareness of all things. St Augustine argues this better than I can, but I hope the point is clear.
So, God doesn't know today what you will do tomorrow. He knows what you are doing tomorrow, because he sees yesterday, today, and tomorrow all as one. Again, I don't see how that has any relevance to the issue of free will.