It has been said that all great thinkers and reformers have worked out and enunciated their main ideas, before they had attained the age of thirty. Be this true or not, it applies to Herbart. The Science of Education, published when he was thirty-two, contains all his chief ideas on education, and the application of psychology thereto, either fully developed or in the germ to be worked out later on. These two books we have been comparing, may thus be said to represent the two ends of the thread of Herbart's life-long educational activity. It is a singular testimony to the power and depth as well as to the ripeness of his intellect, that he should have been able at that early age to formulate a body of educational principles which, proved to be so true, so well founded, and so practical, that5 after thirty years' experience and testing, he found little or no thing to alter, beyond elucidating them and extending their ap plication. And no w, for half a century since his death, other men have continuously entered into his labours, have taken up his ideas and principles, are carrying on the work he began, and still find those principles to be sound, those ideas to be true.