I set down as “imaginary.” And, as a mere subordinate point of view, this may do very well. But it is quite another thing on such a ground to deny existence in the Absolute to every other spatial system. For we have the “imaginary” extension on our hands as a fact which remains, and which should cause us to hesitate. And, when we reflect, we see clearly that a variety of physical arrangements may exist without anything like spatial interrelation. They will have their unity in the Whole, but no connections in space each outside its own proper system of matter. And Nature therefore cannot properly be called a single world, in the sense of possessing a spatial unity.
Thus we might have any number of physical systems, standing independent of spatial relations with each other. And we may go on from this to consider another point of interest. Such diverse worlds of matter might to any extent still act on and influence one another. But, to speak strictly, they could not inter-penetrate at any point. Their interaction, however intimate, could not be called penetration; though, in itself and in its effects, it might involve a closer unity. Their spaces always would remain apart, and spatial contact would be impossible. But inside each world the case, as to penetration, might be different. The penetration of one thing by another might there even be usual; and I will try to show briefly that this presents no difficulty.
The idea of a Nature made up of solid matter, interspaced with an absolute void, has been inherited, I presume, from Greek metaphysics. And, I think, for the most part we hardly realize how entirely this view lies at the mercy of criticism. I am speaking, not of physics and the principles employed by physics, but of what may be called the metaphysics of the literary market-place. And the notion com-
