Forgive the source material, but there's a Star Trek book that sort of addresses this. Picard asks Q, why, as an omnipotent being, does he keep coming around to bug humanity, if he already knows what's going to happen. Q thinks about it for a second, and then replies, if you drop an ice cube in a hot frying pan, you know what the outcome is going to be. What you can't predict is how the cube is going to skitter around and react before it meets it's end. That's the important part. I've always liked that because it reminds of of deterministic randomness (which, in some arguments, combines the deterministic nature of physics of the large, with the random nature of quantum mechanics). Basically, the universe may very well be deterministic. All future states can be derived from the present condition of the system. But, the important part is, it's impossible to predict what a future state might be, meaning it's essentially random. Think of the number pi. We can compute pi to whatever digit we want, like to the 1,000,000,000 digit, and it never changes no matter how many times we compute it. But, we cannot use any of those digits to predict what the 1,000,000,001 digit will be. We can compute it, but until we do, we cannot know it because pi's digits are random.