The modern student has heard so many versions of the story of the two-faced shield that he is much disposed to suspect that many of the questions which have so long divided "philosophers" may be only new illustrations of the old fable, and he asks whether there need be any real antagonism between those who attribute knowledge to experience and those who attribute it to our innate reason. There are men of science who, seeing no good reason to challenge Plato's belief that experience, creating nothing, only calls forth the "ideas" which were already dormant or latent in the mind, do nevertheless find reason to ask whether exhaustive knowledge of our physical history may not some time show how these dormant "ideas" came to be what they are. They ask whether errors may not be judgments which lead us into danger and tend to our physical destruction, and whether it may not be because a judgment has, in the long run, proved preservative in the struggle for existence that we call it true. May not, for example, the difference between the error that the stick half in water is bent and the truth that the stick in air is straight, some time prove to be that the savage who has rectified his judgment has speared his fish, while he who has not has lost his dinner? So long as we can ask such questions as this, how can we be sure that because a judgment is no more than might have been expected from us, as Nature has made us, at our present intellectual level, it is either necessary or ultimate or universal? Things that are innate or natural are not always necessary or universal, for while reason is natural to the mind of man, some men are unreasonable, and a few have been even known to be illogical. It therefore seems clear that another view of the groundwork of science than that set forth by Professor Mivart is possible, for many believe that this groundwork is to be found in our desire to know what we do not yet know, rather than in things known; and they believe they wish to know in order that they may learn to distinguish truth from error, and walk with sure feet where the ignorant grope and stumble. Many books are profitable and instructive even if they fail to convince; and the question which a prospective student of Mivart's book is likely to ask is whether it is consistent with itself; for if the author has not so far made himself master of his subject as to state his case without palpable contradiction, no one will expect much help from him. It is a remark of Aristotle, in the Introduction to the Parts of Animals, that while one may need special training to tell whether an author has proved his point, all may judge whether he is consistent with himself, and the attempt to learn whether Mivart's book is consistent may not greatly tax our minds.