The Historian's series, pt 1

"'Critical history', then, 'must have a criterion'; and it is clear that the criterion can only be the historian himself. The way in which he handles his authorities will and must depend on what he brings to the study of them. Now the historian is a man with an experience of his own; he experiences the world in which he lives; and it is this experience which he brings with him to the interpretation of historical evidence. He cannot be simply a tranquil mirror reflecting what that evidence tells him; until he has exerted himself and laboured to interpret it, it tells him nothing, for in itself it is only 'a host of jarring witnesses, a chaos of disjointed and discrepant narrations'. What he makes out of this welter of material depends on what he is: that is to say, upon the body of experience which he brings with him to work.

--Collingwood, The Idea of History, p.137

Like my friend said, a good historian is never just a historian...