Sounds like determinism, which messed with my head when I read about it. It's the idea that since every action/reaction in the universe follows set rules (including even brain chemistry), theoretically every moment of the future can be predicted, thus making it already written. We'd just be experiencing it under the impression that we had free will, but all of our thoughts and actions would actually just be part of the domino chain.

Luckily quantum physics seems to toss determinism right out the window.