It may be asked what damage will result from evaluation. Passing over grave injustice to individuals, we observe that they must lead to the formation of what Bagehot aptly called a crust, preventing the free development of science. We have been laboring for years to obtain scientific freedom, freedom in teaching, freedom in learning, freedom in expression. For this end many a battle has been fought by noble leaders of thought. Indeed, every new movement of thought has to struggle to make itself felt, and to struggle precisely against those who control the most respectable avenues of publication; against the very ones who would be selected to give expert opinions and make evaluations of literature. Call to mind the opposition to Darwin and Huxley--although they were especially and particularly fortunate in early gaining the adherence of scientific men--also the opposition to Adam Smith, Malthus, Ricardo and John Stuart Mill--and to the last named, even now, some would on a scale of 100 give an evaluation perhaps of 50, others of 65--still others 80 and 90. Recently an economic book appeared of which one widely quoted periodical said that it illustrated a _reductio ad absurdum_ of false tendencies, while another expert opinion inclined to place it among the great works of the age. It would seem to me that if we are to have formal evaluations, they should at least be restricted to works which have been before the public for a period of fifty years. We have in this proposal, as I take it, an attack on liberty, proceeding from one who would not willingly attack it, but illustrating the truth of the saying "Eternal vigilance is the price of liberty." It is proposed to publish virtually an _index librorum prohibitorum_ and an _index expurgatorius_. And of all efforts ever conceived along this line, this is precisely the worst because of its apparently impersonal character. Let the ordinary reader go to a guide and find a book described as unscientific and superficial, and what weight can it have for him. The authority has spoken. It is well enough for librarians personally to guide and direct their constituencies, and one review may be weighed against another review. The old methods even must be used by librarians cautiously, and they are ample for the purpose to be attained. The great point is that there should be a fluid current of opinion, and every facility for a revision of judgment should be maintained. Reviewers themselves change their views. I, myself, remember reviews which I wrote of works by two distinguished American authors, which I now regret, as my estimates were, I believe, not altogether sound and did an injustice to the authors, namely John Fiske and Lester F. Ward. But after all, I suppose no special harm was done, but if extracts from these reviews had been made part of a system of evaluation it would have been different.