And this fact is a mystery, though it may be questioned if it be more mysterious why matter should think of itself, than why it should move of itself.

At any rate, thus far we are all agreed; and whatever mystery we may be dealing with, it is one that leaves us in ignorance but not in doubt.

The doubt comes in at the next step.

We have then not to wonder at one fact, but, the mystery being in either case the same, to choose between two hypotheses.

The first is that there is in consciousness one order of forces only, the second is that there are two.