>[!abstract] >Laplace's demon was a notable published articulation of causal determinism on a scientific basis by Pierre-Simon Laplace in 1814. According to determinism, if someone (the demon) knows the precise location and momentum of every atom in the universe, their past and future values for any given time are entailed; they can be calculated from the laws of classical mechanics. > >Discoveries and theories in the decades following suggest that some elements of Laplace's original writing are wrong or incompatible with our universe. For example, irreversible processes in thermodynamics suggest that Laplace's "demon" could not reconstruct past positions and moments from the current state: A metal rod heated at one end will equilibrate to the same end temperature across the bar regardless of which side was initially heated; reconstructing the initial state from the final state is therefore impossible as multiple initial states all share the same final state ("Laplace's demon", 2025). >[!quote] >“Such an intelligence would embrace in the same formula the movements of the greatest bodies of the universe and those of the lightest atom; for it, nothing would be uncertain and the future, as the past, would be present to its eyes” (Laplace, 1814, as cited in Gleick, 1987). >[!quote] >Une intelligence qui, pour un instant donné, connaîtrait toutes les forces dont la nature est animée, et la situation respective des êtres qui la composent, si d’ailleurs elle était assez vaste pour soumettre ces données à l’analyse, embrasserait dans la même formule les mouvemens des plus grands corps de l’univers et ceux du plus léger atome : rien ne serait incertain pour elle, et l’avenir comme le passé, serait présent à ses yeux (Laplace, 1814). ## Idea compass - **North** (upstream): Newtonian mechanics - **East** (different): Chaos theory; indeterminism; randomness - **South** (downstream): — - **West** (similar): [[Determinism]] ## References - Gleick, J. (1987). *Chaos*. Penguin Books. - Laplace, P.-S. (1814). *Essai philosophique sur les probabilités*. https://fr.m.wikisource.org/wiki/Essai_philosophique_sur_les_probabilit%C3%A9s/1a - Laplace's demon. (2025, March 09). In *Wikipedia*. https://en.wikipedia.org/w/index.php?title=Laplace%27s_demon&oldid=1270108110 ## Related - [[Determinism]]