We cannot delay here to demonstrate the necessity and the inevitability of this subjective criterion in every narrative of human affairs. We will merely say that this criterion is compatible with the utmost objectivity, impartiality, and scrupulosity in dealing with data, and indeed forms a constitutive element of such subjective criterion. It suffices to read any book of history to discover at once the point of view of the author, if he be a historian worthy of the name and know his own business. There exist liberal and reactionary, rationalist and catholic historians, who deal with political or social history; for the history of philosophy there are metaphysical, empirical, sceptical, idealist, and spiritualist historians. Absolutely historical historians do not and cannot exist. Can it be said that Thucydides and Polybius, Livy and Tacitus, Machiavelli and Guicciardini, Giannone and Voltaire, were without moral and political views; and, in our time, Guizot or Thiers, Macaulay or Balbo, Ranke or Mommsen? And in the history of philosophy, from Hegel, who was the first to raise it to a great elevation, to Ritter, Zeller, Cousin, Lewes, and our Spaventa, was there one who did not possess his conception of progress and criterion of judgment? Is there one single work of any value in the history of Aesthetic, which has not been written from this or that point of view, with this or that bias (Hegelian or Herbartian), from a sensualist or from an eclectic point of view, and so on? If the historian is to escape from the inevitable necessity of taking a side, he must become a political and scientific eunuch; and history is not the business of eunuchs. They would at most be of use in compiling those great tomes of not useless erudition, _elumbis atque fracta_, which are called, not without reason, monkish. If, then, the concept of progress, the point of view, the criterion, be inevitable, the best to be done is not to try and escape from them, but to obtain the best possible. Everyone strives for this end, when he forms his own convictions, seriously and laboriously. Historians who profess to wish to interrogate the facts, without adding anything of their own to them, are not to be believed. This, at the most, is the result of ingenuousness and illusion on their part: they will always add what they have of personal, if they be truly historians, though it be without knowing it, or they will believe that they have escaped doing so, only because they have referred to it by innuendo, which is the most insinuating and penetrative of methods. [Sidenote] _Non-existence of a unique line of progress in artistic and literary history._