Laplace's demon

We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.

— Pierre Simon Laplace, A Philosophical Essay on Probabilities[3]

This intellect is often referred to as Laplace's demon (and sometimes Laplace's Superman, after Hans Reichenbach). Laplace himself did not use the word "demon", which was a later embellishment. As translated into English above, he simply referred to: "Une intelligence ... Rien ne serait incertain pour elle, et l'avenir, comme le passé, serait présent à ses yeux." Apparently, Laplace was not the first to evoke one such demon and strikingly similar passages can be found decades before Laplace's Essai philosophique in the work of scholars such as Nicolas de Condorcet and Baron D'Holbach.[4] However, it seems that the first who offered the image of a super-powerful calculating intelligence was Roger Joseph Boscovich, whose formulation of the principle of determinism in his 1758 Theoria philosophiae naturalis turns out not only to be temporally prior to Laplace's but also—being founded on fewer metaphysical principles and more rooted in and elaborated by physical assumptions—to be more precise, complete, and comprehensive than Laplace's somewhat parenthetical statement of the doctrine.[5]

In James Gleick's book, Chaos, the author appears to conflate Laplace's demon with a "dream" for human deterministic predictability, and even states that "Laplace seems almost buffoon-like in his optimism, but much of modern science has pursued his dream" (pg.14).

In the full context of Laplace's Essay it is clear that the demon, as conceived, is infinitely removed from the human mind, and thus could never assist humanity's efforts at prediction:

All these efforts in the search for truth tend to lead [the human mind] back continually to the vast intelligence which we have just mentioned, but from which it will always remain infinitely removed.

— Pierre Simon Laplace, A Philosophical Essay on Probabilities[3]

There has recently been proposed a limit on the computational power of the universe, i.e. the ability of Laplace's demon to process an infinite amount of information. The limit is based on the maximum entropy of the universe, the speed of light, and the minimum amount of time taken to move information across the Planck length, and the figure was shown to be about 10¹²⁰ bits.[13] Accordingly, anything that requires more than this amount of data cannot be computed in the amount of time that has elapsed so far in the universe.

Another theory suggests that if Laplace's demon were to occupy a parallel universe or alternate dimension from which it could determine the implied data and do the necessary calculations on an alternate and greater time line, the aforementioned time limitation would not apply. This position is for instance explained in The Fabric of Reality by David Deutsch, who says that realizing a 300-qubit quantum computer would prove the existence of parallel universes carrying the computation.

Counter arguments to this can be made using string theory. Albeit, the gradients of finite theories are useful, speculative scenarios, such as space-time decompactification[14] occurring on a faster frame, require infinities whose interpretation remains open.

• In the anime series Rampo Kitan: Game of Laplace, Laplace's Demon is the basis of a high school student's computer program called Dark Star. Dark Star is a program which allows for a masked vigilante, Twenty Faces, to cause the deaths of people who have escaped justice.

• In the anime series Darwin's Game, the character of Rein has the super power (or "sigil" as it is called within the show) of 'Laplace' which allows her to predict the future based on any information she is aware of.

• In Blast of Tempest, chaos theory and the butterfly effect are incorporated into the main theme, where time travel and breaking out of parallel universes become the main plot.

• In the film Waking Life a discussion of Laplace's Demon takes place, as well as a handling of the retort from Quantum Mechanics.

• In the webcomic Dresden Codak, this concept is used in a page melding philosophical notions and a Dungeons and Dragons séance titled "Advanced dungeons and discourse".[15] In this page, Kimiko Ross has to burn the second law of thermodynamics in order to summon the demon.

• The UK sitcom Spaced featured an episode called "Chaos", in which the artist Brian makes an implicit reference to Laplace's Demon in a conversation about chaos theory. He states that reality is a mathematically predictable preordained system, even though it would "utterly defy any possibility of comprehension by even the most brilliant human mind."

• In the light novel and anime series Seishun Buta Yarou wa Bunny Girl Senpai no Yume wo Minai, it is mentioned in order to try define the situation in which the main protagonist is repeating a specific day.

• Rapurasu no Majo (Laplace's Witch), a 2015 novel by Japanese author Keigo Higashino. It was adapted into a 2018 film directed by Takashi Miike and starring Shō Sakurai.

• Shin Megami Tensei: Devil Survivor, a 2009 tactical role playing game for the Nintendo DS, makes reference to the thought experiment with the plot-point of "Laplace Mail", an automated e-mail system that predicts upcoming events for the coming day.

• In Rozen Maiden by Peach-Pit, Laplace No Ma (Laplace's demon) is a character that prompts the Rozen Maidens' mission with riddles, and appears only in the N-field. He looks like a white rabbit in a tuxedo but acts more like the Cheshire Cat, an obvious play on both characters from "Alice's Adventures in Wonderland".

• In Adam Fawer's Improbable: A Novel, the main character becomes a personification of Laplace's demon.

• Laplace No Ma (Laplace's Demon) is a 1993 video game for the SNES.

• The Masoukishin Cybuster from the Super Robot Wars metaseries possesses the 'Laplace's Demon Computer' which gives it the ability to predict the future as well as editing/altering events in the timeline itself. A similar (though less powerful) device is used by another giant robot, the Unicorn Gundam.

• The Italian mystery film Il demone di Laplace ("Laplace's demon") revolves around a group of simulation software developers invited to a strange island laboratory by an incognito scientist mastermind that has seemingly achieved total prediction powers.

• In the FX show Devs, a secretive Silicon Valley company constructs a powerful quantum computer that can simulate the complete state of the universe, with the ability to visualize any moment in time with video and audio.

• Clockwork universe theory
• Eudaemons
• Maxwell's demon