 Mersenne did not extend his voluntarism to mathematical truths, as Descartes did in a rather unconventional way. The confrontation of Mersenne’s and Descartes’s positions on this theme has been the object of some discussions in the secondary literature—see especially Marion 1980; Dear 1988; Carraud 1994; Fabbri 2008. Descartes first assertions on God’s creation of mathematical truths appeared in a letter to Mersenne of April 15, 1630. Descartes enjoined his correspondent to tell everyone aloud that the mathematical truths that Mersenne called eternal were not independent of God, but “have been created by him and depend on him entirely just as do all the other creatures” (Descartes to Mersenne, April 15, 1630, AT I: 145). God freely established them, and impressed them in the minds of men, as a king would in his kingdom. The statement seems to have surprised Mersenne. The Minim’s own letters are lost, but this can be inferred from the fact that Descartes in May and June 1630, obviously answers repeated requests for clarification: