The zest, the generous affections, the illusions, the despair, all the traditional attributes of Youth – all save this – come and go with us through life; again and again in riper years we experience, under a new stimulus, what we thought had been finally left behind, the authentic impulse to action, the renewal of power and its concentration on a new object; again and again a new truth is revealed to us in whose light all our previous knowledge must be rearranged.