  How successful is Vaihinger in resolving the alleged tensions in Kant’s critical philosophy? On one level, straightforwardly rejecting things in themselves and endorsing an ontology only of sensations clearly avoids the supposed problem of attributing causal efficacy to transcendent objects. On another, however, it would appear that Vaihinger cannot so easily reject things in themselves without causing problems for his basic epistemological view. For one, an obvious question arises as to what it is that has the sensational contents that serve as Vaihinger’s ontological basics. For another, we have seen that Vaihinger’s arguments in the Introduction hold that the mind or “psyche” operates on sensory stimuli, and that it has certain ends to which fictions are expedient means. If nothing exists except sensations, then it seems we must read Vaihinger’s talk of ‘mind’ loosely, perhaps as referring to some particular kind of collection of or relation between sensations. But, one is tempted to say, it is simply incoherent to suggest that sensations themselves are the bearers of sensations, that they have aims, that they operate on and systematize other sensations, etc. At the very least, “operation” would seem to be a causal notion, so that Vaihinger’s causal fictionalism threatens to undermine the arguments at the foundation of his system. Vaihinger sometimes attempts to respond to these sorts of worries. He suggests, for example, “From our point of view the sequence of sensations constitutes ultimate reality, and two poles are mentally added, subject and object” (PAO 56); “nothing exists except sensations which we analyze into two poles, subject and object … . In other words, the ego and the ‘thing in itself’ are fictions” (PAO 44). The question of course is who the we is here that is doing the mental adding. Perhaps Vaihinger intends such talk to itself be fictional. But he cannot hold that without undermining the very motivation for his fictionalism. Nor does Vaihinger ever make clear and precise exactly what “poles” of sensations are supposed to be.