The other danger is that of sacrificing brightness and charm of presentation. When an effort is made to avoid generalisations, and to squeeze into the narrative as many facts as the space will admit, the narrative is apt to become dry, because compression involves the curtailment of the personal and dramatic element. These are the rocks between which every historian has to steer. If he has ample space, he does well to prefer the course of giving all the salient facts and leaving the reader to generalise for himself. If, however, his space is limited, as must needs be the lot of those who write a universal history, the impossibility of going into minute detail makes generalisations inevitable, for it is through them that the result and significance of a multitude of minor facts must be conveyed in a condensed form. [Sidenote: New Minds and New Facts] All the greater, therefore, becomes the need for care and sobriety in the forming and setting forth every summarising statement and general conclusion or judgment. Probably the soundest guiding principle and best safeguard against error is to be found in shunning all preconceived hypotheses which seek to explain history by one set of causes, or to read it in the light of one idea. The habit of magnifying a single factor, such as the social factor, or the economic, or the religious, has been a fertile source of weakness in historical writing, because it has made the presentation of events one-sided, destroying that balance and proportion which it is the highest merit of any historian to have attained. Theory and generalisation are the life-blood of history. They make it intelligible. They give it unity. They convey to us the instruction which it always contains, together with so much of practical guidance in the management of communities as history is capable of rendering. But they need to be applied with reserve, and not only with an impartial mind, but after a painstaking examination of all the facts--whether or no they seem to make for the particular theory stated--and of all the theories which any competent predecessor has propounded. For the historian, though he must keep himself from falling under the dominion of any one doctrine by which it is sought to connect and explain phenomena, must welcome all the light which any such doctrine can throw upon facts. Even if such a doctrine be imperfect, even if it be tainted by error, it may serve to indicate relations between facts, or to indicate the true importance of facts, which previous writers had failed to observe, or had passed too lightly over. It is thus that history always needs to be re-written. History is a progressive science, not merely because new facts are constantly being discovered, not merely because the changes in the world give to old facts a new significance, but also because every truly penetrating and original mind sees in the old facts something which had not been seen before.