of appearances, it is rational that evil should
exist. Show us this, and evil is explained. Explanation of a thing,
then, means showing that the thing is rational. Now we can ask that
everything else in the world should be shown to be rational. But we
cannot demand that the philosopher shall show that reason is rational.
This is absurd. Reason is what is already absolutely rational. It is
what explains itself. It is its own reason. It is a self-explanatory
principle. This, then, must be the principle of which we are in
search. The Absolute, we said, must be a self-explanatory principle,
and there is only one such, namely, reason. The Absolute, therefore,
is reason.

It was the greatness and glory of Plato to have seen this, and thereby
to have become the founder of all true philosophy. For to say that the
Absolute is concepts is the same as saying it is reason. It might
seem, then, that Plato has satisfied the second canon of criticism. He
takes as first principle a self-explanatory reality. But we cannot
quite so quickly jump to this conclusion. After all, the mere word
reason is not a key which will unlock to us the doors of the universe.
Something more is necessary than the mere word. We must, in fact, be
told what reason is. Now there are two senses in which we might ask
the question, what reason is, one of which is legitimate, the other
illegitimate. It is illegitimate to ask what reason is, in the sense
of asking that it shall be explained to us in terms of something else,
which is not reason. This would be {242} to give up our belief that
reason is its own reason. It would be to seek the reason of reason in
something which is not reason. It would be to admit that reason, in
itself, is not rational. And this is absurd. But it is legitimate to
ask, what reason is, meaning thereby, what is the _content_ of reason.
The content of reason, we have seen, is concepts. But what concepts?
How are we to know whether any particular concept is part of the
system of reason or not? Only, it is evident, by ascertaining whether
it is a rational concept. If a concept is wholly rational, then it is
a part of reason. If not, not. What we need, then, is a detailed
account of all the concepts which reason contains, and a proof that
each of these concepts is really rational. It is obvious that only in
this way can we make a satisfactory beginning in philosophy. Before we
can show that reason explains, that is, rationalizes the world,