In many of the comments which his lectures have called out in the newspapers one meets every now and then with a curious failure to comprehend the position which an average non-scientific man occupies in such a conflict as in now going on over the doctrines of evolution. Professor Huxley was very careful not to repeat the error which delivered Professor Tyndall into the hands of the enemy at Belfast. He expressed no opinion as to the nature of the causal force which called the world into existence. He did not profess to know anything about the sources of life. He consequently did not once place himself on the level of the theologian or the unscientific spectator. What he undertook to do and did was to present to the audience some specimens of the evidence by which evolutionists have been led to the conclusion that their theory is correct. Now, the mistake which a good many newspaper writers--some of them ministers--have made in passing judgment on the lectures lies in their supposing that this evidence must be weak and incomplete because _they_ have not been convinced. There is probably no more widely diffused fallacy, or one which works more mischief in all walks of life, than the notion that it is only those whose business it is to persuade who need to be trained in the art of proof, and that those who are to be persuaded need no process of preparation at all. The fact is that skill in reasoning is as necessary on the one side as the other. He cannot be fully and rightly convinced who does not himself know how to convince, and no man is competent to judge in the last resort of the force of an argument who is not on something like an equality of knowledge and dialectical skill with the person using it. This is true in all fields of discussion; it is pre-eminently true in scientific fields. Of course, therefore, the real public of the scientific man--the public which settles finally whether he has made out his case--is a small one. Outside of it there is another and larger one on which his reasoning may act with irresistible force; but just as the fact that it does so act does not prove that his hypothesis is true, so also the fact that it has failed to convince proves nothing against its soundness. In other words, a man's occupying the position of a listener does not necessarily clothe him with the attributes of a judge, and there may be as much folly and impertinence in his going about saying, "I do not agree with Huxley; he has not satisfied me; he will have to produce more proof than that before I believe in evolution," as in going about saying, "I know as much about evolution as Huxley and could give as good a lecture on it as he any day." And yet a good many people are guilty of the one who would blush at the mere thought of the other.