But if there is a principle in common, and often similar methods justifying a comparison that can be found in no other form of history, it should not be forgotten that this principle, prohibiting the historian from involving himself in any way in the actions or words, conforms also to that principle of the strictest objectivity. Actions and words are the material of tragedy, but also of scientific observation. And the subtlety of literary means may, as a result, be used in the service of truth.