The best way to understand the Meditations is through the lens of Descartes's theistic metaphysics rather than via his programme for physical science. This applies to his use of the concept of ‘nature’ in the Sixth Meditation, which serves Descartes's goal of theodicy. In working this out, Descartes reaches a conclusion about the functional role of sensory perception that is, paradoxically, not far from that offered by Darwinian naturalism. So far from being inherently geared to tracking the truth, the role of sensation is linked to its survival value for the organism. In virtue of his theistic metaphysics however, Descartes is able to set this conclusion against the background of other cognitive faculties that are in principle accurate detectors of the truth; the absence of such a resource for modern Darwinian naturalists creates difficulties for the presumption that humans are cognitively equipped to search for the truth.