Most of the great changes in the world's history come about gradually and wise men can see them coming, for it is very hard to run counter to the nature of average men, and all great advances and degradations of society are the result of persistent causes; but a few times, since our records have been kept, there has arisen a single genius, who has done what no number of lesser men could accomplish, who has upset theories as well as dominions, preached a new faith, discovered some new application of Force which has given a fresh start to the world in its weary and perplexed struggle for a higher life. These few great men have so changed the current of affairs that we may safely say they have modified the future of the whole human race. At any rate they have taught us what might and dignity is attainable by man and has so given us ideals by which the commonest of us can estimate his worth and exalt his aspirations. So, too, there have been gigantic criminals and imperial fools who have wrecked the peace of the world and caused the "ape and tiger" elements, which were repressed by long and anxious struggles, to break out afresh in their savagery.