To say “the soul exists” is to say that, within us, there's a principle – distinct from matter and perceptible by the senses – whereby we understand our states of consciousness. Does such a principle really exist? In our lectures on psychology, we argued that extended matter is but an appearance, the real substratum of which can be conceived only by analogy with the forces that we ourselves are. So there's no need to ask if the principle to which the states of consciousness are connected is material in nature. Nothing can be extended, for the idea of extension is contradictory. In fact, it's quite possible that the principle perceived by our senses as material in nature is actually identical to the principle perceived by our consciousness as spirit. Still, to say that the soul is spiritual is to say that it's distinct from extended, perceptible matter.

Our theory of the world's universal spirituality is sufficient to demonstrate that this is indeed the nature of the soul. Yet the claim that this is so is also supported by four more specific arguments – the first three of which reveal a contradiction between the nature of spirit and that of matter:

1. Spirit has unity – this we've established in several ways in our discussion of psychology. Matter, by contrast, is multiple and infinitely divisible. In matter, no fundamental unity can be found beyond which division can't proceed. So matter can't be identical to spirit.

2. […]