It's literally just the belief that the universe is a closed, predictable system without any actually chaotic elements. Therefore, everything is a result of the things that preceded it in one massive causal chain going back to the Big Bang and before.

There's some stuff at the most fundamental levels of physics that chaos is one hypothesis for but there's no current reason to privilege that hypothesis over others, and in any case once you get above the subatomic level things start behaving incredibly predictably again.