We republish this pamphlet, honestly believing that on all questions affecting the happiness of the people, whether they be theological, political or social, fullest right of free discussion ought to be maintained at all hazards. We do not personally indorse all that Dr. Knowles says: his "Philosophical Proem" seems to us full of philosophical mistakes, and--as we are neither of us doctors--we are not prepared to indorse his medical views; but since progress can only be made through discussion, and no discussion is possible where differing opinions are suppressed, we claim the right to publish all opinions, so that the public, enabled to see all sides of a question, may have the materials for forming a sound judgment. The alterations made are very slight, the book was badly printed, and errors of spelling and a few clumsy grammatical expressions have been corrected; the subtitle has been changed, and in one case four lines have been omitted, because they are repeated word for word further on. We have, however, made some additions to the pamphlet, which are in all cases kept distinct from the original text. Physiology has made great strides during the past forty years, and not considering it right to circulate erroneous physiology, we submitted the pamphlet to a doctor in whose accurate knowledge we have the fullest confidence, and who is widely known in all parts of the world as the author of the "Elements of Social Science;" the notes signed "G. B." are written by this gentleman. References to other works are given in foot-notes for the assistance of the reader, if he desires to study up the subject further. Old Radicals will remember that Richard Carlile published a work entitled "Every Woman's Book," which deals with the same subject and advocates the same object as Dr. Knowlton's pamphlet R. D. Owen objected to the "style and tone" of Carlile's "Every Woman's Book," as not being in "good taste," and he wrote his "Moral Physiology" to do in America what Carlile's work was intended to do in England. This work of Carlile's was stigmatized as "indecent" and "immoral," because it advocated, as does Dr. Knowlton's, the use of preventive checks to population. In striving to carry on Carlile's work, we cannot expect to escape Carlile's reproach; but, whether applauded or condemned, we mean to carry it on, socially as well as politically and theologically.