History in a general sense is concerned with past human events. But it does not consider them simply as bare facts succeeding each other in the unrolling of time; it gathers them together as vital parts of a variegated and complex unity and deals not merely with the subject matter of these events, but with their cause and effect, by which they are welded into a whole. The historian, who is both scientist and artist, must gather the seemingly chaotic and accidental succession of events into a synthesis. Knowledge must always ultimately unite; and it is in this process of unification that the Catholic historian is bound to differ from any other kind of historian.

The past events with which the historian is dealing are human events, not the eruptions and radiations of the mineral world, not the burgeonings and seeding of the vegetable world, not the fights and amours of the animal kingdom, but the successive actions of MAN. Man is the subject of this science and so it is in man that we may find the guiding principles of historical unity. Certainly we are not here concerned immediately with the nature of man. That is the field of psychology which considers man according to his constitution with his intellect and his will. Nevertheless, the historian depends essentially upon rational psychology to describe to him the nature of man, as well as upon revelation itself to give a concrete view of that nature. The silversmith must understand the nature of the metal he proposes to work.