 By design, the constructive arguments of the Meditations unfold even though the meditator remains in doubt about being awake. This of course reinforces the ongoing theme that perfect knowledge does not properly encompass judgments of external sense. (The judgment that an external corporeal world exists is not strictly a judgment of external sense – as if knowing its existence simply by sensing it. Rather, as we’ve seen, the judgment arises from an complex inference about the possible causes of sensations.) In the closing paragraph of the Sixth Meditation, Descartes revisits the issue of dreaming. He claims to show how, in principle – even if not easily in practice – it is possible to achieve perfect knowledge that one is presently awake.