H. P. Grice Finds A. M. Quinton's Thought-Experiment "Hardly Thought Out"

Space is ordinarily seen to be a unique individual. All real things are contained in one and the same space, and all spaces are part of the one space. In principle, every place can be reached from every other place by traveling through intermediate places. The spatial relation is symmetrical. Grice’s friend, A. M. Quinton devised a thought experiment to challenge this picture. Suppose that we have richly coherent and connected experience in our dreams just as we have in waking life, so that it becomes arbitrary to claim that our dream experience is not of an objectively existing world like the world of our waking experience. If the space of my waking world and my dream world are not mutually accessible, it is unlikely that we are justified in claiming to be living in a single spatially isolated world. Hence, space is not essentially singular. In assessing this account, we might distinguish between systematic and public physical space and fragmentary and private experiential space. The two-space myth raises questions about how we can justify moving from experiential space to objective space in the world as it is. “We can at least conceive circumstances in which we should have good reason to say that we know of real things located in two distinct spaces.” Quinton, “Spaces and Times,” Philosophy 37