R. Osgood Mason, M.D., was a Fellow of the New York Academy of Medicine.
Boston Transcript: "He repudiates the idea of the supernatural altogether, and in this he is in accord with the best thought of the day. ...Interesting and logical."
Hartford Courant: "The work of a scientist and not of a crank. ...Fascinating reading."
New York Times: "The curious matter he treats about, he presents in an interesting manner."
Nation: "A popularly written book ... A not inconsiderable contribution to psychical research."
Chicago Tribune: "Certain to attract wide attention ... Thoroughly interesting ... The spirit of his work is such as to deserve respectful attention from every scientific mind."