As we try to think away all the objects which space contains, we must not forget to think away the light with which we unconsciously fill all space. We shall find if we succeed in this admittedly difficult exercise, that space itself will then disappear. Thus the common belief in space as a kind of vast vessel containing everything, as depending on and being determined by the distances between two or more objects and the relative positions occupied by these objects, is hardly a correct one. Both "inside" and "outside" are merely relative terms. All this again is because, as mentalism declares, space is really the idea which we subconsciously impose on. Hence, when for a few brief moments the mind transcends its creations and returns to itself in mystical abstraction, we lose the feeling of the "outsideness" of things and the world fades into being our own unreal dream. This happens because, as mentalism has already taught us, space is needed by the mind to contain its images, to measure its forms, and therefore mind accordingly makes it. Now the same considerations apply to time, for if we think away all the objects which have their life in the past present or future, there will be no time left to flow onwards. There will be no independent thing called time. Nevertheless, the mind is not left in a wholly negative state after this is done. Whatever we may possibly experience or know in the external world must necessarily be experienced or known under the forms of space and time; to be at all, they have to be as they are. But these forms are variable and changeable, relative and dependent. Therefore these events or things are not themselves eternal and enduring realities. Space and time are ways in which we experience existence; they are not things in themselves.
-- Notebooks Category 19: The Reign of Relativity > Chapter 4: Time, Space, Causality > # 55
-- Perspectives > Chapter 19: The Reign of Relativity > # 2