Hacker News Reader

The best demon would simply answer "you intend to do the opposite of whatever I tell you." - this would most accurately define the future state of the universe.

Alternatively, the demon could say one thing, and send a delayed timestamped message with the opposite.

View on HN

This. Constraining the demon to two responses can't work. The demon needs to be able to give an answer with at least as much information as the entire universe's state -- not yes or no answers. The issue with the person only exists because the person's actions cannot be represented with a single bit of information. But the person cannot hope to outsmart the demon if it's response has more bits of information than the person can possibly respond with.

I think the best summary is:

The disproof assumes free will, but Laplace's universe assumes free will is an illusion. Devise an experiment to work out which is right -- a Laplace demon, if such a thing can exist, is probably a good experiment to test this.

Reply on news.ycombinator.com