 Voluntarism concerning the nature and laws of creation may appear as an important common ground that Mersenne shared with orthodox (Thomist) scholasticism, and with Descartes. As Lenoble has shown, its assertion was an essential precondition for the establishment of a mechanical science, unifying the whole of nature under the contingent will of God, his initial decisions regarding the distribution and laws of matter and motion. Mersenne’s voluntarism implies that physics is not about an eternal and immutable object, as God could have ordered the word in various manners and with various laws. This, as we shall see, has important epistemological consequences: God’s freedom means that he is not compelled to create things in the simplest fashion. This is evidenced in the reign of the grace, where one can clearly see that God did not chose the shortest way to dispense his grace, as he could have assured our salvation with a unique act of his will (cf. Questions Inouïes, p. 344–5] But this hold as well for scientific truths, and explains for example why Mersenne never considered as decisive Galilean and Copernican arguments for the motion of the earth taken from the simplicity of natural order. Mersenne’s point was actually quite close to the argument from divine omnipotence that Pope Urban VIII suggested to Galileo in 1623, and that Galileo, somewhat ironically, put in the mouth of Simplicio in the concluding sentences of the 1632 Dialogo: Man cannot presume to know how the world really is, since God could have brought about the same effects in ways unimagined by humans (see Galileo, 1890–1909, VII, 488).