" Whatever, therefore, and however much, our concept of an object may contain, we must go outside it, if we are to ascribe existence to the object. In the case of objects of the senses, this takes place through their connection with some one of our perceptions, in accordance with empirical laws. But in dealing with objects of pure thought, we have no means whatsoever of knowing their existence, since it would have to be known in a completely a priori manner. Our consciousness of all existence (whether immediately through perception, or mediately through inferences which connect something with perception) belongs exclusively to the unity of experience; any [alleged] existence outside this field, while not indeed such as we can declare to be absolutely impossible, is of the nature of an assumption which we can never be in a position to justify.33 "
― C.G. Jung , Psychological Types