Apparently (and I hope the physicists will weigh in on this) it means:
"Wolpert proves that in any [...] system of universes, quantities exist that cannot be ascertained by any inference device inside the system. Thus, the “demon” hypothesized by Pierre-Simon Laplace in the early 1800s (give the demon the exact positions and velocities of every particle in the universe, and it will compute the future state of the universe) is stymied if the demon must be a part of the universe."
http://jonesthought.wordpress.com/category/mathematics/ 
