Some of us, doubtless, have often wondered why the heavenly jerusalem is described in the book of revelations as a cube ; "the length and the breadth and the height of it are equal." this is because the cube is the figure of perfect stability, and thus represents truth, which can never be overthrown. turn it on what side you will, it still remains the perfect cube, always standing upright; you cannot upset it. this figure, then, represents the manifestation in concrete solidity of that central life-giving energy, which is not itself any one plane but generates all planes, the planes of the above and of the below and of all four sides. but it is at the same time a city, a place of habitation ; and this is because that which is "the within" is living spirit, which has its dwelling there.