Principles of Philosophy

book by Descartes

Principles of Philosophy (Latin: Principia philosophiae) is a book by René Descartes. It is basically a synthesis of the Discourse on the Method and Meditations on First Philosophy.


  • Cogito, ergo sum.
    • I think, therefore I am.
    • Variant: I think therefore I exist.
    • Principia philosophiae, Part I, Article 7
  • Ex nihilo nihil fit.
    • Nothing comes out of nothing.
    • Principia philosophiae, Part I, Article 49
  • That the nature of a body does not consist in weight, hardness, color, or other similar properties; but in extension alone. By so doing, we shall perceive that the nature of matter... does not consist in... affects of the senses... but only in the fact that it is a thing possessing extension in length, breadth, and depth.
    • Principia philosophiae, Part II, Article 4

See also

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