, kindling his own personal lamp at that central sunlike radiance,
retired straightway into his laboratory of whatsoever kind and found it
truly illuminated for the first time. His lamp seemed to be of two
flames enwrapped as one; a baleful and a benign. Whenever it shone upon
anything that was true, it made this stand out the more clear,
valuable, resplendent. But wherever it uncovered the false, it darted
thereat a swift tongue of flame, consuming without mercy the ancient
rubbish of the mind. Vast purification of the world by the fire of
truth! There have been such purifications before; but never perhaps in
the history of the race was so much burned out of the intellectual path
of man as during the latter half of the nineteenth century.

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. Th