We have to seek for sources of another kind in this than in political history. There historians are the fountainheads, which again have as sources the deeds and sayings of individuals; and the historians who are not original have over and above performed their work at secondhand. But historians always have the deeds already present in history, that is to say, here brought into the form of ordinary conception; for the name of history has two meanings: it signifies on the one hand the deeds and events themselves, and on the other, it denotes them in so far as they are formed through conception for conception. In the history of Philosophy there are, on the contrary, not any sources which can be derived from historians, but the deeds themselves lie before us, and these—the philosophic operations themselves—are the true sources. If we wish to study the history of Philosophy in earnest, we must go to such springs as these. Yet these operations form too wide a field to permit of our keeping to it alone in this history. In the case of many philosophers it is absolutely necessary to confine oneself to the original authors, but in many periods, in which we cannot obtain original sources, seeing that they have not been preserved to us, (as, for instance, in that of the older Greek philosophy) we must certainly confine our attention simply to historians and other writers. There are other periods, too, where it is desirable that others should have read the works of the philosophers and that we should receive abstracts therefrom. Several schoolmen have left behind them works of sixteen, twenty-four and twenty-six folios, and hence we must in their case confine ourselves to the researches of others. Many philosophic works are also rare and hence difficult to obtain. Many philosophers are for the most part important from an historic or literary point of view only, and hence we may limit ourselves to the compilations in which they are dealt with. The most noteworthy works on the history of Philosophy are, however, the following, regarding which I refer for particulars to the summary of Tennemann’s History of Philosophy, by A. Wendt, since I do not wish to give any complete list.