There is a sort of land which receives in autumn, year by year, the deposit of its own dead leaves and weeds and grasses without either the winds and waters to clear these away or the soil to reabsorb and reconvert them into the materials of reproduction. Thus year by year the land tends farther toward sterility by the very accumulation of what was once its life. But send a forest fire across those smothering strata of vegetable decay; give once more a chance for every root below to meet the sun above; for every seed above to reach the ground below; soon again the barren will be the fertile, the desert blossom as the rose. It is so with the human mind. It is ever putting forth a thousand things which are the expression of its life for a brief season. These myriads of things mature, ripen, bear their fruit, fall back dead upon the soil of the mind itself. That mind may be the mind of an individual; it may be the mind of a century, a race, a civilization. To the individual, then, to a race, a civilization, a century, arrives the hour when it must either consume its own dead or surrender its own life. These hours are the moral, the intellectual revolutions of history. The new science must not only clear the stagnant ground for the growth of new ideas, it must go deeper. Not enough that rubbish should be burned: old structures of knowledge and faith, dangerous, tottering, unfit to be inhabited longer, must be shaken to their foundations. It brought on therefore a period of intellectual upheaval and of drift, such as was once passed through by the planet itself. What had long stood locked and immovable began to move; what had been high sank out of sight; what had been low was lifted. The mental hearing, listening as an ear placed amid still mountains, could gather into itself from afar the slip and fall of avalanches. Whole systems of belief which had chilled the soul for centuries, dropped off like icebergs into the warming sea and drifted away, melting into nothingness. The minds of many men, witnessing this double ruin by flame and earthquake, are at such times filled with consternation: to them it seems that nothing will survive, that beyond these cataclysms there will never again be stability and peace--a new and better age, safer footing, wider horizons, clearer skies. It was so now. The literature of the New Science was followed by a literature of new Doubt and Despair. But both of these were followed by yet another literature which rejected alike the New Science and the New Doubt, and stood by all that was included under the old beliefs. The voices of these three literatures filled the world: they were the characteristic notes of that half-century, heard sounding together: the Old Faith, the New Science, the New Doubt. And they met at a single point; they met at man's place in Nature, at the idea of God, and in that system of thought and creed which is Christianity.