He who would truly know what the doctrine of evolution is, and to what it leads, must literally begin at the beginning. He must free his mind from the cant of agnosticism and from the cant of belief. He must refuse to accept dogmas on the authority of any one, be they the dogmas of the scientist, or of the theologian. He must learn that his mental nature is placed under certain laws, as surely as his corporeal structure; and he must cheerfully obey the necessities which compel him to accept some conclusions and to reject others. Keeping his reasoning powers in a well-balanced condition, he must prove all things, holding fast to that which is in conformity with sound deduction, and to that alone. But all persons may not be able to afford the time to pursue truth in this way, or may not have the facilities for the requisite research. It seemed to me, therefore, that an effort to do for them what they can not do for themselves would be acceptable to a great many people. It may be objected that the imaginary philosopher whom I have introduced in some of my chapters under the name of Sophereus, or the searcher after wisdom, debating the doctrines of evolution with a supposed disciple of that school, whom I have named Kosmicos, is an impossible person. It may perhaps be said that the conception of a man absolutely free from all dogmatic religious teaching, from all bias to any kind of belief, and yet having as much knowledge of various systems of belief as I have imputed to this imaginary person, would in modern society be the conception of an unattainable character. My answer to this criticism would be that I felt myself at liberty to imagine any kind of character that would suit my purpose. How successfully I have carried out the idea of a man in mature life entirely free from all preconceived opinions, and forming his beliefs upon principles of pure reason, it is for my readers to judge. With regard to the other interlocutor in the dialogues, I hope it is not necessary for me to say that I do not impute all of his opinions or arguments to the professors of the evolution school, or to any section of it. He is a representative of the effects of some of their teachings, but not an individual portrait. But as, for the purposes of the antagonism, it was expedient to put into the mouth of this person whatever can be said in favor of the hypothesis of evolution, it became necessary to make him represent the dogmatic side of the theory; and thus to make the collision and contrast between the minds of the two debaters as strong as I could. Controversial discussion in the form of debate has been used from the time of Plato. While I have adopted a method, I have not presumed to imitate its great exemplars. But for the value of that method I shall presently cite weighty testimony. It was a relief to me to resort to it after having pursued the subject in the more usual form of discussion; and indeed it forced itself upon me as a kind of