Laplace's Demon is absurd

Jared Lorince writes:

Instead we are built to operate with limited time, processing power, and available information. To imagine a truly rational human being, one unbounded by these constraints, is to imagine nothing short of a Laplacean demon. For those unfamiliar with the term, it references the hypothetical super-intelligence proposed by French mathematician Pierre-Simon Laplace, capable of knowing the state of every atom in the universe, and associated with the first published description of scientific determinism.

He refers to Laplace’s demon, a fanciful idea that is surprisingly widely believed. Lorince is just attacking the idea that humans can be all-knowing, but I attack the idea that such knowledge can even exist in a mathematically defined form.

Physicists might argue that if you only knew the quantum state function of the universe at some time in the past, then you could apply some unitary operator to get the state at future times. To believe anything else is contrary to a scientific worldview, they say. Occasionally this sort of thinking will drive them to deny free will or to accept multiple universes.

I say that Laplace's Demon is absurd. It is a huge unwarranted assumption. Nobody has ever explained how it would work. It seems contrary to what we know about quantum mechanics. My FQXi essay explains why I think it is wrong.