the insane explanation, if not conclusive, is at least unanswerable;
this may be observed specially in the two or three commonest kinds
of madness. If a man says (for instance) that men have a conspiracy
against him, you cannot dispute it except by saying that all the men
deny that they are conspirators; which is exactly what conspirators
would do. His explanation covers the facts as much as yours.
Or if a man says that he is the rightful King of England, it is no
complete answer to say that the existing authorities call him mad;
for if he were King of England that might be the wisest thing for the
existing authorities to do. Or if a man says that he is Jesus Christ,
it is no answer to tell him that the world denies his divinity;
for the world denied Christ's.

Nevertheless he is wrong. But if we attempt to trace his error
in exact terms, we shall not find it quite so easy as we had supposed.
Perhaps the nearest we can get to expressing it is to say this:
that his mind moves in a perfect but narrow circle. A small circle
is quite as infinite as a large circle; but, though it is quite
as infinite, it is not so large. In the same way the insane explanation
is quite as complete as the sane one, but it is not so large.
A bullet is quite as round as the world, but it is not the world.
There is such a thing as a narrow universality; there is such
a thing as a small and cramped eternity; you may see it in many
modern religions. Now, speaking quite externally and empirically,
we may say that the strongest and most unmistakable MARK of madness
is this combination between a logical completeness and a spiritual
contraction. The lunatic's theory explains a large number of things,
but it does not explain them in a large way. I mean that if you
or I were dealing with a mind that was growing morbid, we should be
chiefly concerned not so much to give it arguments as to give it air,