Bonn 2010 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 6: History and Philosophy of Physics

AGPhil 6.3: Talk

Thursday, March 18, 2010, 15:15–15:45, JUR G

Euler on the impenetrability of bodies and the liberty of spirits — •Dieter Suisky — Institut für Physik, Humboldt-Universität zu Berlin, e-mail: dsuisky@physik.hu-berlin.de

In 1760, Euler commented on the difference between spirits and bodies: "But spirits are of a very different nature, and their actions depend on principles directly opposite. Liberty, entirely excluded from the nature of body, is an essential portion of spirit. A spirit without liberty would no longer be a spirit, as a body without extension or impenetrability would no longer be a body."
It will be demonstrated that Euler modified the conceptual background Leibniz presented in the metaphor of the two labyrinths, that of liberty and necessity and that of continuity and indivisibles involving the notion of infinity. Contrary to Leibniz, who stressed the differences between spirits, Euler accentuated the equality between individuals based on the ability of spirits to make decisions. This is considered as the origin of sin. Bodies cannot deviate in their motions from God’s decrees whereas spirits can. This essential issue had been traced back to the controversy between Augustine and Pelagius [Euler, Lettres]. Independently of the individuality, Euler assigned the same responsibility to every person. Likewise independently of the mass, Euler assigned the same impenetrability to every body which is, in case of interaction, considered as the origin of forces. Though in opposition to each other, the notions are mutually connected and the equality of spirits is introduced as a fundamental internal principle. All subsequently assigned differences are to be based upon this fundament.