Descartes' Principles of Philosophy (Renati Descartes Principiorum philosophiae pars I et II, more geometrico demonstratae) is the only work that Baruch Spinoza published during his lifetime, under his own name, in Amsterdam in 1663 (editor J. Rieuwertsz).
Written at the request of a student, it takes up the Principles of Philosophy of Descartes (1644) by exposing them according to geometric order (more geometrico), the same method as that which he would later use in Ethics. It is accompanied by an appendix, Metaphysical Thoughts (Cogitata metaphysica), where Spinoza clearly deviates from Cartesianism —notably on creation, will and soul — and anticipates his later theses. Written in Latin, it is today considered as a work in its own right by Spinoza, not as a simple gloss by Descartes.