In the

history of science The history of science covers the development of science from ancient times to the present. It encompasses all three major branches of science: natural, social, and formal. Science's earliest roots can be traced to Ancient Egypt and Meso ...

, Laplace's demon was a notable published articulation of

causal determinism Determinism is a philosophical view, where all events are determined completely by previously existing causes. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping motives and cons ...

on a scientific basis by

Pierre-Simon Laplace Pierre-Simon, marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French scholar and polymath whose work was important to the development of engineering, mathematics, statistics, physics, astronomy, and philosophy. He summarize ...

in 1814. According to determinism, if someone (the demon) knows the precise location and

momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass ...

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 Classical mechanics is a physical theory describing the motion of macroscopic objects, from projectiles to parts of machinery, and astronomical objects, such as spacecraft, planets, stars, and galaxies. For objects governed by classi ...

. This idea states that “free will” is merely an illusion, and that every action previously taken, currently being taken, or that will take place was destined to happen from the instant of the big bang. 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 momenta from the current state.

English translation

This intellect is often referred to as ''Laplace's demon'' (and sometimes ''Laplace's Superman'', after

Hans Reichenbach Hans Reichenbach (September 26, 1891 – April 9, 1953) was a leading philosopher of science, educator, and proponent of logical empiricism. He was influential in the areas of science, education, and of logical empiricism. He founded the ''Ges ...

). 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."'' This idea seems to have been widespread around the time that Laplace first expressed it in 1773, particularly in France. Variations can be found in

Maupertuis Pierre Louis Moreau de Maupertuis (; ; 1698 – 27 July 1759) was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Prussian Academy of Science, at the ...

(1756), Nicolas de Condorcet (1768),

Baron D'Holbach Paul-Henri Thiry, Baron d'Holbach (; 8 December 1723 – 21 January 1789), was a French-German philosopher, encyclopedist, writer, and prominent figure in the French Enlightenment. He was born Paul Heinrich Dietrich in Edesheim, near L ...

(1770), and an undated fragment in the archives of

Diderot Denis Diderot (; ; 5 October 171331 July 1784) was a French philosopher, art critic, and writer, best known for serving as co-founder, chief editor, and contributor to the '' Encyclopédie'' along with Jean le Rond d'Alembert. He was a promi ...

. Recent scholarship suggests that the image of a super-powerful calculating intelligence was also proposed by Roger Joseph Boscovich in his 1758 ''Theoria philosophiae naturalis''.

Arguments against Laplace's demon

Thermodynamic irreversibility

According to chemical engineer

Robert Ulanowicz Robert Edward Ulanowicz ( ) is an American theoretical ecologist and philosopher of Polish descent who in his search for a ''unified theory of ecology'' has formulated a paradigm he calls ''Process Ecology''. He was born September 17, 1943 in Bal ...

, in his 1986 book ''Growth and Development'', Laplace's demon met its end with early 19th century developments of the concepts of irreversibility,

entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodyna ...

, and the

second law of thermodynamics The second law of thermodynamics is a physical law based on universal experience concerning heat and energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects (or "downhill"), unle ...

. In other words, Laplace's demon was based on the premise of reversibility and classical mechanics; however, Ulanowicz points out that many thermodynamic processes are irreversible, so that if thermodynamic quantities are taken to be purely physical then no such demon is possible as one could not reconstruct past positions and momenta from the current state. Maximum entropy thermodynamics takes a very different view, considering thermodynamic variables to have a statistical basis which is separate from the deterministic microscopic physics. However, this theory has met criticism regarding its ability to make predictions about physics; a number of physicists and mathematicians, including Yvan Velenik of the Department of Mathematics for the

University of Geneva The University of Geneva (French: ''Université de Genève'') is a public research university located in Geneva, Switzerland. It was founded in 1559 by John Calvin as a theological seminary. It remained focused on theology until the 17th centur ...

, have pointed out that maximum entropy thermodynamics essentially describes our knowledge about a system but does not describe the system itself.

Quantum mechanical irreversibility

Due to its canonical assumption of

determinism Determinism is a philosophical view, where all events are determined completely by previously existing causes. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping motives and cons ...

, Laplace's demon is incompatible with the Copenhagen interpretation, which stipulates indeterminacy. The interpretation of quantum mechanics is still very much open for debate and there are many who take opposing views (such as the Many Worlds Interpretation and the de Broglie–Bohm interpretation).

Chaos theory

Chaos theory Chaos theory is an interdisciplinary area of scientific study and branch of mathematics focused on underlying patterns and deterministic laws of dynamical systems that are highly sensitive to initial conditions, and were once thought to hav ...

is sometimes pointed out as a contradiction to Laplace's demon: it describes how a deterministic system can nonetheless exhibit behavior that is impossible to predict: as in the butterfly effect, minor variations between the starting conditions of two systems can result in major differences. While this explains unpredictability in practical cases, applying it to Laplace's case is questionable: under the strict demon hypothesis all details are known—to infinite precision—and therefore variations in starting conditions are non-existent. Put another way: Chaos theory is applicable when knowledge of the system is imperfect, whereas Laplace's demon assumes perfect knowledge of the system, therefore the variability leading to chaos in chaos theory and non-variability in the knowledge of the world Laplace's demon holds are noncomparable.

Cantor diagonalization

In 2008, David Wolpert used Cantor diagonalization to challenge the idea of Laplace's demon. He did this by assuming that the demon is a computational device and showed that no two such devices can completely predict each other. Wolpert's paper was cited in 2014 in a paper of Josef Rukavicka, where a significantly simpler argument is presented that disproves Laplace's demon using Turing machines, under the assumption of free will.

Additional context

In full context Laplace's demon, as conceived, is infinitely removed from the human mind and thus could never assist humanity's efforts at prediction: Despite this, the English

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

Stephen Hawking said in his book, '' A Brief History of Time'', that "Laplace suggested that there should be a set of scientific laws that would allow us to predict everything that would happen in the universe." Similarly 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).

Recent views

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. 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. A simple logical proof of the impossibility of Laplace's idea was advanced in 2012 by Iegor Reznikoff, who posits that the demon cannot predict his own future memory..

References

{{DEFAULTSORT:Laplace's Demon Epistemology Thought experiments Pierre-Simon Laplace