To understand is not simply difficult, it is also endless. But this fact does not make it hopeless. The understanding of history grows by what it feeds on, enlarges itself with every fresh success, constantly reveals more to be understood. Our illustrations may serve us again. From the accessible records of the battle of Marathon we can understand with tolerable success the immediate antecedents and consequents of that great event. But in calling the event great we do not simply eulogize its participants. We indicate, rather, that its antecedents and consequents have been far-reaching and momentous. Greece, we say, was saved. But what are we to understand by that salvation? To answer we must write and rewrite her own history, the history of what she has been and is; and with every fresh writing the battle of Marathon becomes better understood. It becomes a different battle with a different truth. And more than this: with every rewriting we understand better what went before and what followed after until the battle itself becomes but the symptom of deeper things. So, too, is it with Europe's present struggle. Already its history has begun with many volumes. Following the example of Thucydides in the Peloponnesian war, men are writing it contemporaneously by summers and winters. The consequences they can only guess at, but they have done much with the antecedents, so much that the last fifty years of Europe are better understood than they were a year ago. The record of them has changed little; our understanding of them has changed much. It has changed so much that they have already become a different half-century from what they were. The truth about them last year is not the truth about them to-day. Fifty years hence what will the truth about them be?