Primitive notions are most familiar from the celebrated letters Descartes exchanged with Princess Elisabeth of Bohemia on the topic of mind-body interaction, but they figure prominently in many of Descartes’ writings. Descartes sometimes introduces them as notions orideas, making it is clear that either word is acceptable (e.g., AT III 691, CSMK 226; cf. AT VII 440, CSM II 296 and AT VIIIB 358, CSM I 303). In the early Rules for the Direction of the Mind, he refers to “primary seeds of truth [prima veritatum semina] naturally implanted in human minds” (AT X 376, CSM I 18; cf. The World AT XI 47, CSM 2 97). The “seeds of truth which are naturally in our souls” return in the Discourse on Method (1637) as “primary truths” (AT VI 64, 76; CSM I 144, 150). In the first of the famous pair of letters to Elisabeth, Descartes crucially relies on primitive notions (notions primitives), also called “simple notions” (notions simples), that the soul “possesses by nature” as “ready-made” (AT III 666–67, CSMK 219). And in the letter to Voetius written at the same time as the exchange with Elisabeth, we again have “notions” that are “innate” in virtue of being “implanted” in the soul (AT VIIIB 166, CSM I 222). In the Principles of Philosophy, the principles referred to in the title are characterized in much the same way. They can be clearly and distinctly perceived or intuited, and they enable the deduction of “all other things” (AT IXB 9–11, CSM 1 183–84). This treatment of principles is not surprising given that the words translated as “primitive,” “primary,” and “principle” can be synonymous in both Latin and French. Finally, in August 1649, less than half a year before his death, Descartes makes use of primitive notions in a letter to More (AT V 402–3, CSMK 381).

Despite these continuities, Descartes does not settle on an exact characterization of primitive notions, nor does he supply a detailed and absolutely complete inventory. It is abundantly clear that primary notions are innate, but this affords little help because Descartes’ treatment of innate ideas is notoriously difficult.