As I hold presence of mind, or what is called courage, to be precisely proportioned to familiarity with the circumstances that lead to it, so I should say that I had been long sufficiently familiar with all experiments that appertain to the marvellous.  I had witnessed many very extraordinary phenomena in various parts of the world,—­phenomena that would be either totally disbelieved if I stated them, or ascribed to supernatural agencies.  Now, my theory is that the supernatural is the impossible, and that what is called supernatural is only a something in the laws of Nature of which we have been hitherto ignorant.  Therefore, if a ghost rise before me, I have not the right to say, “So, then, the supernatural is possible;” but rather, “So, then, the apparition of a ghost, is, contrary to received opinion, within the laws of Nature,—­that is, not supernatural.”

Now, in all that I had hitherto witnessed, and indeed in all the wonders which the amateurs of mystery in our age record as facts, a material living agency is always required.  On the Continent you will find still magicians who assert that they can raise spirits.  Assume for the moment that they assert truly, still the living material form of the magician is present; and he is the material agency by which, from some constitutional peculiarities, certain strange phenomena are represented to your natural senses.

Accept, again, as truthful, the tales of spirit-manifestation in America,—­musical or other sounds; writings on paper, produced by no discernible hand; articles of furniture moved without apparent human agency; or the actual sight and touch of hands, to which no bodies seem to belong,—­still there must be found the medium, or living being, with constitutional peculiarities capable of obtaining these signs.  In fine, in all such marvels, supposing even that there is no imposture, there must be a human being like ourselves by whom, or through whom, the effects presented to human beings are produced.  It is so with the now familiar phenomena of mesmerism or electro-biology; the mind of the person operated on is affected through a material living agent.  Nor, supposing it true that a mesmerized patient can respond to the will or passes of a mesmerizer a hundred miles distant, is the response less occasioned by a material being; it may be through a material fluid—­call it Electric, call it Odic, call it what you will—­which has the power of traversing space and passing obstacles, that the material effect is communicated from one to the other.  Hence, all that I had hitherto witnessed, or expected to witness, in this strange house, I believed to be occasioned through some agency or medium as mortal as myself; and this idea necessarily prevented the awe with which those who regard as supernatural things that are not within the ordinary operations of Nature, might have been impressed by the adventures of that memorable night.