The full title of the first edition (1641) of Descartes’ most renowned work was Meditations on First Philosophyin Which the Existence of God and the Immortality of the Soul Are Demonstrated. On the basis of this title one would expect to find within that text equal effort devoted to proving the immortality of the soul and to proving the existence of God. Yet, while the latter is given abundant treatment in two separate meditations (3 and 5), neither the noun immortalitas nor the adjective immortale appears even once in any of the six meditations. Appropriately, the title of the second edition (1642) of the Meditations lacked any explicit reference to immortality and promised only to demonstrate, in addition to the existence of God, “the distinction between the human soul and the body.”

There is good reason to ask, therefore, at least in the case of the Meditations, whether Descartes intended to offer any rational support for belief in the immortality of the soul. A negative response to this question is suggested by epistolary evidence that Descartes himself did not choose to mention immortality in the title of the 1641 Meditations but that Mersenne was responsible for the inclusion: “I am finally sending you [Mersenne] my work on metaphysics, which I have not yet put a title to, so that I can make you its godfather and leave the baptism to you” (AT III 238–39; CSMK 158; see Fowler 1999, 35–53, for the debate on this authorship). However, it will become clear from texts undeniably penned by Descartes that he intended early in his career to prove the immortality of the soul and that he eventually believed that he had offered the strongest possible demonstration for immortality.

A decade before publishing the Meditations, in 1630, Descartes expressed to Mersenne his eagerness to complete a “little treatise of Metaphysics” wherein he “set out principally to prove the existence of God and of our souls when they are separate from the body, from which their immortality follows” (AT I 182, CSMK 29).