Thirdly, as one of the circumstances that render it difficult to comprehend Plato’s own speculative thought, we can scarcely reckon the external consideration that in his Dialogues he does not speak in his own person, but introduces Socrates and many others as the speakers, without always making it plain which of them expresses the writer’s own opinion. By reason of this historic circumstance, which seems to bear out the manysidedness of Plato, it has of course been often said, by ancients as well as moderns, that he merely expounded, from a historical point of view, the system and doctrine of Socrates, that he adapted much in the Dialogues from various Sophists, and avowedly advanced many theorems belonging to an earlier date, especially those of the Pythagoreans, Heraclitics, and Eleatics, even adopting, in the last case, the Eleatic mode of treatment. Hence it was said that to these philosophies the whole matter of the treatise belonged, the outward form alone being Plato’s. It is therefore necessary to distinguish what is peculiarly his and what is not, or whether the component parts are in harmony. In the Socratic Dialogues that we have from Cicero, the personages can be much more readily made out; but in Cicero there is nothing of real interest offered to us. With Plato there can be no talk of this ambiguity, and the difficulty is only in appearance. In the Dialogues of Plato his philosophy is quite clearly expressed; they are not constructed as are the conversations of some people, which consist of many monologues, in which one person expresses a certain opinion and another person differs from him, and both hold to their own way of thinking. Here, on the contrary, the divergency of opinions which comes out is examined, and a conclusion arrived at as to the truth; or, if the result is negative, the whole process of knowledge is what is seen in Plato. There is, therefore, no need to inquire further as to what belongs to Socrates in the Dialogues, and what belongs to Plato. This further observation we must, however, make, that since Philosophy in its ultimate essence is one and the same, every succeeding philosopher will and must take up into his own, all philosophies that went before, and what falls specially to him is their further development. Philosophy is not a thing apart, like a work of art; though even in a work of art it is the skill which the artist learns from others that he puts into practice. What is original in the artist is his conception as a whole, and the intelligent use of the means already at his command; there may occur to him in working an endless variety of ideas and discoveries of his own. But Philosophy has one thought, one reality, as its foundation; and nothing can be put in the place of the true knowledge of this already attained; it must of necessity make itself evident in later developments. Therefore, as I have already observed (Vol. I. p. 166), Plato’s Dialogues are