Principia Philosophiae constitutes the most comprehensive book that Descartes ever wrote. He calls it his “philosophy.” The text combines an exposition of Cartesian metaphysics with an exposition of his physics, itself unparalleled in the rest of Descartes’ corpus. Without a doubt, the scope of the work explains the interest that will be shown in it by other thinkers of the early modern period, such as Spinoza and Leibniz, who will take the first two parts of this text as a basis, first, to give a systematic account of Descartes’ thought (Spinoza's Principles of Descartes’ Philosophy) and, second, to criticize its fundamental principles (Leibniz's Critical Remarks on Descartes’ Principles). For all the stress placed by recent scholarship on the Meditations, to many of his contemporaries Descartes was primarily the author of the Principles.

The genesis of this text clarifies the stakes. In November 1640, Descartes announces to Mersenne his intention to prepare a “complete textbook of my philosophy” (AT III 233, CSMK 157), which he conceives of as a competitor to the philosophy of the schools (i.e., the philosophy, nurtured by Aristotle, taught in Jesuit schools). At that time, Descartes is still preparing to publish the Meditations: he has just completed the First Set of Replies to Objections (see Objection and Replies). But, in July 1640, the Jesuit Pierre Bourdin publicly criticizes the Dioptrics, which acutely irritates Descartes: “I am going to become engaged in a war with the Jesuits. Their mathematician in Paris has publicly attacked my Optics in his theses, and I have written to his superior with a view to involving the whole Society in this quarrel” (AT III 103, CSMK 151). This is the origin of the work that was to become the Principles.

Fortunately, a relative truce is established as a result of Bourdin's commitment to formulate objections to the Meditations. Descartes receives these objections in January 1642. They concern principally the method of doubt, the real distinction between mind and body, and the existence of God. He published this Seventh Set of Objections and Replies in the second edition of the Meditations (May 1642), accompanied by the Letter to Father Dinet (Descartes’ former teacher and Bourdin's superior in the Jesuit order), in which he publicly announced his determination to publish his “philosophy.” The Latin Principles was published in July 1644.