Stevenson has somewhere one of his perfectly picked phrases for an empty-minded man; that he has not one thought to rub against another while he waits for a train.

The Moslem had one thought, and that a most vital one; the greatness of God which levels all men.

But the Moslem had not one thought to rub against another, because he really had not another.
It is the friction of two spiritual things, of tradition and invention, or of substance and symbol, from which the mind takes fire.
The creeds condemned as complex have something like the secret of sex; they can breed thoughts.
An idealistic intellectual remarked recently that there were a great many things in the creed for which he had no use.
He might just as well have said that there were a great many things in the _Encyclopedia Britannica_ for which he had no use.
It would probably have occurred to him that the work in question was meant for humanity and not for him.

But even in the case of the _Encyclopedia_, it will often be found a stimulating exercise to read two articles on two widely different subjects and note where they touch.

In fact there is really a great deal to be said for the man in _Pickwick_ who read first about China and then about metaphysics and combined his information.
But however this may be in the famous case of Chinese metaphysics, it is this which is chiefly lacking in Arabian metaphysics.
They suffer, as I have said of the palm-tree in the desert, from a lack of the vitality that comes from complexity, and of the complexity that comes from comparison.