 The objects of dreams and hallucinations don’t meet the criterion of actuality of the Second Postulate, that is, according with the laws of causality. Thus while in Berkeley’s view the esse of spatial things consists in their being perceived by the senses, for Kant they are the objects of the correct causal/scientific account of the contents of our outer experience. This causal criterion allows that a spatial object, or, more precisely, the matter from which it is constituted, is (at least relatively) permanent – which would seem ruled out in Berkeley’s position, since the spatial object does not last any longer than the idea does. (Berkeley does say that the ideas of what “are called real things” differ from “those excited in the imagination” by “being less regular, vivid, and constant” (Berkeley 1710, Principles Part I, 33), but for him this difference does not challenge or undermine the claim that the esse of a physical object is its percipi.) None of this forces a metaphysical realist as opposed to an idealist reading of Kant.