Even with perfect knowledge in a purely deterministic universe, not all futures are computable. E.g. see [Undecidable_problem][1] So it's not merely **practically** impossible to build a perfect predictor for such cases. The existence of a so called "Counter", something that would use the prediction to do the opposite, makes it **logically** impossible to calculate the future in that situation. If it were logically possible in theory to create a prediction in such a situation, determinism could not logically be true. Since such a prediction is logically impossible, it's concept does not logically make determinism impossible. The idea of the mentioned paradox is not new, online articles discuss this referencing a paper from 1968 by Michael Scriven and is called "Scrivens paradox". Wikipedia has no article on this, i might just start one. The intuition that in a deterministic universe perfect knowledge means predictability can be found as [Laplace's demon][2] Mainstream philosophy holds that likely our universe is not 100% deterministic, but free will would still be possible even if it was 100% deterministic (Compatibilism). [1]: https://en.wikipedia.org/wiki/Undecidable_problem [2]: https://en.m.wikipedia.org/wiki/Laplace%27s_demon