Pierre-Simon de Laplace
An intellect knowing all forces and positions would see the future like the past.
Life
Pierre-Simon Laplace (1749-1827), a French mathematician and astronomer, gave celestial mechanics its classical form and built a large part of probability theory. In his Philosophical Essay on Probabilities he presents the world as wholly governed by laws: an intellect that knew all forces and all positions would see the future like the past. That image became the symbol of determinism.
Main works
Explains the motion of the solar system by Newton's gravitation alone.
Founds the calculus of probability on mathematical analysis.
Argues that chance comes from our ignorance of causes and sets out the idea of an intellect that could foresee everything.
In his own words
« We must therefore regard the present state of the universe as the effect of its earlier state and as the cause of the one that will follow. »
« An intelligence which, at a given instant, knew all the forces by which nature is animated and the respective situation of the beings that compose it, if it were vast enough to submit these data to analysis, would embrace in one formula the movements of the greatest bodies of the universe and those of the lightest atom: nothing would be uncertain for it, and the future, like the past, would be present to its eyes. »
« The curve described by a single molecule of air or vapour is regulated as certainly as the orbits of the planets: the only difference between them is that which our ignorance puts there. »
Positions
click a row to see the evidenceHe explains nature by laws alone without ever denying God in his writings; he is called a deist or an agnostic. The line "I had no need of that hypothesis" is a doubtful anecdote.
Laplace, Exposition du système du monde (1796) ; R. Hahn, Pierre Simon Laplace (2005)
Our ignorance of causes is why we need probabilities: most of what we know is only probable, not certain.
Laplace, Essai philosophique sur les probabilités (1814)
All events, human acts included, follow from prior states by fixed laws, so an intellect knowing everything would foresee them all.
Laplace, Essai philosophique sur les probabilités (1814)