nay, in a sense it is infinitely reasonable, just as a threepenny
bit is infinitely circular. But there is such a thing as a mean
infinity, a base and slavish eternity. It is amusing to notice
that many of the moderns, whether sceptics or mystics, have taken
as their sign a certain eastern symbol, which is the very symbol
of this ultimate nullity. When they wish to represent eternity,
they represent it by a serpent with his tail in his mouth. There is
a startling sarcasm in the image of that very unsatisfactory meal.
The eternity of the material fatalists, the eternity of the
eastern pessimists, the eternity of the supercilious theosophists
and higher scientists of to-day is, indeed, very well presented
by a serpent eating his tail, a degraded animal who destroys even himself.

This chapter is purely practical and is concerned with what
actually is the chief mark and element of insanity; we may say
in summary that it is reason used without root, reason in the void.
The man who begins to think without the proper first principles goes mad;
he begins to think at the wrong end. And for the rest of these pages
we have to try and discover what is the right end. But we may ask
in conclusion, if this be what drives men mad, what is it that keeps
them sane? By the end of this book I hope to give a definite,
some will think a far too definite, answer. But for the moment it
is possible in the same solely practical manner to give a general
answer touching what in actual human history keeps men sane.
Mysticism keeps men sane. As long as you have mystery you have health;
when you destroy mystery you create morbidity. The ordinary man has
always been sane because the ordinary man has always been a mystic.
He has permitted the twilight. He has always had one foot in earth
and the other in fairyland. He has always left himself free to doubt
his gods; but (unlike the agnostic of to-day) free also to believe