The truth is that the ideal of the natural sciences, instead of being the perfection, is one of the many crises that historical thought has passed through and will pass through. Historical thought is dialectic of development, and not by any means a deterministic explanation by means of causes which does not explain anything because it does not develop anything. But whatever we may think of this, it is certain that naturalism--that is, the criticism of naturalism--can alone supply the clue for unravelling the web of the historiography of the last ten years; the same events and historical movements enumerated above have acted in the particular way in which they have acted owing to being constantly framed in naturalistic thought. For the rest, nothing forbids, and it may even serve a useful purpose, that the history of philosophy and the history of historiography should receive literary treatment in different books, for altogether practical reasons, such, for instance, as the abundance of material and the different training and acquirements needed for the treatment of the different classes of material. But what is _apparently disunited_ by practice thought _really_ unifies; and this real unification is what I have wished to inculcate, without the pedantic idea ever passing through my mind of dictating rules for composing books, as to which it is desirable to leave all liberty of inclusion and exclusion to writers, in conformity with their various intentions. [1] _Charakteristik der antiken Historiographie_ (Berlin, 1833). [2] _Geschichte der neueren Historiographie_ (München u. Berlin, Oldenburg, 1911). [3] _Geschichte der historischen Forschung und Kunst seit der Wiederherstellung der literarischen Cultur in Europa_ (Göttingen, 1812-20). II GRÆCO-ROMAN HISTORIOGRAPHY