explain itself. It cannot be a principle which itself still requires
explanation by something else. If it is itself not self-explanatory,
but is an ultimate mystery, then even if we succeed in deducing the
universe from it, nothing is thereby explained. This, for example, is
precisely the defect of materialism. Even if we suppose it proved that
all things, including mind, arise from matter, yet the objection
remains that this explains nothing at all, for matter is not a
self-explanatory existence. It is an unintelligible mystery. And to
reduce the universe to an ultimate mystery is not to explain it.
Again; some people think that the world is to be explained by what
they call a "first cause." But why should any cause be the first? Why
should we stop anywhere in the chain of causes? Every cause is {67}
necessarily the effect of a prior cause. The child, who is told that
God made the world, and who inquires who, in that case, made God, is
asking a highly sensible question. Or suppose, in tracing back the
chain of causes, we come upon one which we have reason to say is
really the first, is anything explained thereby? Still we are left
with an ultimate mystery. Whatever the principle of explanation is, it
cannot be a principle of this kind. It must be a principle which
explains itself, and does not lead to something further, such as
another cause. In other words, it must be a principle which has its
whole being in itself, which does not for its completeness refer us to
anything beyond itself. It must be something fully comprehended in
itself, without reference to anything outside it. That is to say, it
must be what we call self-determined or absolute. Now any absolute
principle must necessarily be one. Suppose that it were two. Suppose
you attempt to explain the world by two principles, X and Y, each of
which is ultimate, neither being derived from the other. Then what
relation does X bear to Y? We cannot fully comprehend X without
knowing its relation to Y. Part of the character and being of X is
constituted by its relation to Y. Part of X's character has to be
explained by Y. But that is not to be self-explained. It is to be
explained by something not itself. Therefore, the ultimate explanation
of things must be one.

The Eleatics, then, were perfectly correct in saying that all is one,
and that the ultimate principle of the universe, Being, is one. But if
we examine the way in which they carried out their monism, we sha