After some wholesome criticisms devoted to the "recognition" of materialized forms, and the very true statement (p. 509) that "a very small error in perception may sometimes lead to a very large error of inference," Miss Johnson ends her remarkably interesting paper with two illustrations--one a hallucination (?)[31] induced by false association of ideas; the other an incident in her own experience, occurring at a seance with Eusapia Palladino. Both of these are of importance, and should be studied carefully. Count Solovovo on the contrary considers it somewhat in favour of the hallucination theory that hands were found to melt in the sitters' grasp, when they were forcibly retained (p. 441). I cannot agree with this. It is a different thing to say that hallucination might account for the facts, and saying that the facts tell in favour of hallucination. Chance might account for an experimental apparition, but the fact that the apparition occurred does not prove it to be chance. One must be careful to distinguish facts and inferences, in a case of this character. Whether or not the hands were hallucinatory will depend, not upon _a priori_ probability, or the fact they were visible to some, invisible to others, (for all this might just as well be accounted for on the opposing theory), but upon the fact that, so far as we know, there is no analogy whatever between this oft-recorded event and any of the phenomena of suggestion known to us. If we offer a theory to explain certain facts, it must not only explain them in a rational manner, but must dovetail into what we know--into _the known_. That is the whole method of science. If, therefore, a man advances "hallucination" as an explanation of such facts as those under discussion, he must show how it is that hallucination might be supposed to work: he must bring forward some analogies and examples of somewhat similar instances in order to have a case at all. In science, we cannot speculate _in vacuo_, but must connect with what is already known, if we wish to be scientific at all. What analogies, then, have we that spirit-hands, similar to those described, can be created by suggestion; and that suggestion can cause a number of investigators, at various times, in various places, to believe that these hands melted in theirs while they were trying to retain them?