As to the comparisons between arithmetic and philosophy, chemistry and philosophy, etc., they rest wholly upon a false parallel, and involve a total failure to comprehend the nature of philosophic truth, and its fundamental difference from arithmetical, chemical, or physical truth. If Eratosthenes thought the circumference of the earth to be so much, whereas it has now been discovered to be so much, then the later correct view simply cancels and renders nugatory the older view. {viii} The one is correct, the other incorrect. We can ignore and forget the incorrect view altogether. But the development of philosophy proceeds on quite other principles. Philosophical truth is no sum in arithmetic to be totted up so that the answer is thus formally and finally correct or incorrect. Rather, the philosophical truth unfolds itself, factor by factor, in time, in the successive systems of philosophy, and it is only in the complete series that the complete truth is to be found. The system of Aristotle does not simply cancel and refute that of Plato. Spinoza does not simply abolish Descartes. Aristotle completes Plato, as his necessary complement. Spinoza does the same for Descartes. And so it is always. The calculation of Eratosthenes is simply wrong, and so we can afford to forget it. But the systems of Plato, Aristotle, Spinoza, Leibniz, etc., are all alike factors of the truth. They are as true now as they were in their own times, though they are not, and never were, the whole truth. And therefore it is that they are not simply wrong, done with, finished, ended, and that we cannot afford to forget them. Whether it is not possible to bring the many lights to a single focus, to weld the various factors of the truth into a single organic whole or system, which should thus be the total result to date, is another question. Only one such attempt has ever been made, but no one will pretend that it is possible to understand it without a thorough knowledge of all previous systems, a knowledge, in fact, of the separate factors of the truth before they are thus combined into a total result. Besides, that attempt, too, is now part of the history of philosophy!