It would have been impossible for Epes Sargent to write a bad or valueless book. His careful treatment, his vast range of reading, and his keen power of analysis were sufficient to guarantee valuable results when he undertook to deal with any of the psychical problems that were vexing the public mind. It has always seemed to me, however, that the Proof Palpable is the least satisfactory of his three works, and that, for reasons which it was impossible for the author to control, as well as from some defects in the handling of a very difficult subject. For, at the time when the book was compiled, the subject was not ripe for treatment. It was occupying public attention in a marked manner, but it was beset with difficulties on every side, and the methods of investigation were lax to a reprehensible degree. The various experiments of Mr. Crookes with Florence Cook, of Dr. Wolfe with Mrs. Hollis, of Colonel Olcott with the Eddy Brothers, and of various observers with Mrs. Andrews of Moravia (to say nothing of the still earlier and more completely satisfactory records of Mr. Livermore to which I have already referred), had aroused and excited public attention. But a rank crop of fraudulent imitations soon sprung up, and a subject, inherently mysterious and occult, was discredited by obvious chicanery and palpable fraud. In the midst of this mass of imposture, credulity, and ill-balanced enthusiasm, when conclusions the most tremendous were drawn from evidence insufficient to satisfy a jury in a case of petty larceny, the facts were overshadowed and lost to sight.
At the very time when the book was ready for publication, it became necessary to defer its issue in consequence of Mr. Dale Owen's withdrawal of his published testimony to the materialization phenomena which he had witnessed in Philadelphia. Dr. H. T. Child, who had the most intimate knowledge of the Holmeses publicly threw them over. The Philadelphia Katie King was widely believed to be a discredited fraud, even after General Lippitt and Colonel Olcott had to some extent rehabilitated her. It was, therefore, an unfortunate time to select for the exposition of evidence which was just then tarnished; and for the presentation of theories at best but hastily framed to account for phenomena, which had as yet been imperfectly observed, and then only under extremely unsatisfactory conditions.
Nor can I think that the inherent difficulties of the subject, complicated as they were by accidents of the passing hour, were successfully met by the volume, valuable as it unquestionably is, which at last saw the light. Its very name seems scarcely happy. For, surely, the presentation, even under unimpeachable conditions, of any number of "forms," images, eidola, or whatever name best fits these "counterfeit presentments" of humanity, is no Proof Palpable of Immortality. It may be that evidence is given of the building up of a human form by a process of materialisation. But how does that prove anybody's immortality? It may be that from the body of the medium a "vaporous cloud" has been seen, in rare cases, to issue, condense, and assume a material human form. But he would be a rash man who would undertake to say what that new "form" may be; whether it possesses any separate individuality, and if so, of what nature; whether it is the double of the medium, as some maintain; a too clever elementary, as others allege; or a departed human spirit temporarily revisiting the earth on which it once existed....
–The Psychological Review, Volume 4