 As presented by Kant, the Refutation is aimed at the ‘problematic idealism of Descartes’, who holds that the existence of objects outside us in space is ‘doubtful and indemonstrable’ (Kant 1781/1787 B274)—where, as Kant famously remarks in the Preface to the second edition of the Critique in which he comments on the Refutation, ‘it always remains a scandal of philosophy and universal human reason that the existence of things outside us (from which we after all get the whole matter for our cognitions, even for our inner sense) should have to be assumed merely on faith, and that if it occurs to anyone to doubt it, we should be unable to answer him with a satisfactory proof’ (Kant 1781/1787 Bxxxix note).  Kant’s strategy in response then sets the canonical pattern for a transcendental argument, in beginning from what the skeptic takes for granted, namely that we have mental states which we experience as having a temporal order, and then arguing for the transcendental claim that experience of this sort would not be possible unless we also had generally veridical experience of things in space outside us, and thus knowledge of the external world. In more detail, the argument can be presented as follows (cf. Kant 1781/1787 B275–79 and Bxxxix–xli note):