There were sober epochs when the pursuit of positive knowledge absorbed every one capable of intellectual labour. Or perhaps there were epochs in which men who sought something other than positive science were condemned to universal contempt, and passed unregarded: in such an epoch Plato would have found no sympathy, but would have died in obscurity. One thing at least is clear. He whose chief interest and motive in life is in undemonstrable truths is doomed to complete or relative sterility in the sense in which the word is generally understood. If he is clever and gifted, men may perhaps be interested in his mind and talent, but they will pass his work with indifference, contempt, and even horror; and they will begin to warn the world against him. 'Look at him, my children, He is stern and pale and lean. He is poor and naked, And all men count him mean.' Has not the work of the prophets who sought for ultimate truths been barren and useless? Did life hold them in any account? Life went its own way, and the voices of the prophets have been, are, and ever will be, voices in the wilderness. For that which they see and know, cannot be proved and is not capable of proof. Prophets have always been isolated, dissevered, separate, helpless men, locked up in their pride. Prophets are kings without an army. For all their love to their subjects, they can do nothing for them, for subjects respect only those kings who possess a formidable military power. And--long may it be so! _The Limits of Reality_