natural science so highly valued by you and by me, as authorities in this province. In order to be able to speak with authority concerning any phenomena, one must possess a thorough critical knowledge of the same. Authorities in the present case, therefore, are only such persons as either possess mediumistic powers or, without claiming to be bearers of such properties, are able to produce phenomena of the same nature. As an authority I would therefore acknowledge Mr. Slade, if he possessed scientific credibility, and also by all means Herr Bellaihini, prestidigitateur in Berlin, who, as is well known, has declared in favor of Mr. Slade, if I could premise in his case that he had a conception of the scientific scope of this question. The only person of whom this is true, and who, at the same time, has successfully imitated many of the Slade experiments, is Dr. Christiani, assistant in the Physiological Institute in Berlin. Dr. Christiani, however, declares his experiments to be mere pieces of jugglery. Now, Herr Christiani is certainly not able to imitate all of Mr. Slade's experiments; but he only professes to be an amateur in a field which Mr. Slade cultivates professionally.
I come to my second question: What influence may we concede to outside authority upon our own knowledge? In the immensely preponderant majority of the things which we hold for certain, we all follow the authority of other men; we know only a proportionally small number of facts from our own investigation. Yet all that we owe to foreign authority passes for the more certain the more it agrees with our observation. If a new fact is communicated to us, the investigation of which we are not ourselves in a position to control, then, at least according to the principles hitherto authoritative in science, two criteria must be satisfied, if we are to hold the same to be true: First, it must be confirmed by a credible person, who is master of the field concerned; and, secondly, it must not contradict other established facts. Now, you will probably urge here that this second criterion is an exceedingly fluctuating one. Indeed, various spiritualistic authors have not failed to adduce a multitude of instances from the history of science, in which a fact was at first rejected as false or even impossible, and was yet at last proved to be true. But I beg to call your attention to the fact that, in all these instances, the tertium comparationis with the case before us consists simply and solely in the fact that something was asserted by some scholars and denied by others. This case still occurs of course repeatedly, and the controversy is always decided in favor of those whose observations stand in contradiction with no other established fact. Usually, indeed, the best passport which a discoverer gives to his new observation consists precisely in his indication of its agreement with other facts. I have looked in vain through the whole history of science for a case in which a scientific authority came forward with the assertion of having discovered a new fact, at the same time adding to this assertion the assurance that
