Should this little book fall into the hands of any to whom the occasional use of such terms constitutes a difficulty, I can only apologize to them and refer them for these preliminary explanations to any elementary Theosophical work, such as Mrs. Besant's Ancient Wisdom or Man and His Bodies. The truth is that the whole Theosophical system hangs together so closely, and its various parts are so interdependent, that to give a full explanation of every term used would necessitate an exhaustive treatise on Theosophy as a preface even to this short account of clairvoyance.

Before a detailed explanation of clairvoyance can usefully be attempted, however, it will be necessary for us to devote a little time to some preliminary considerations, in order that we may have clearly in mind a few broad facts as to the different planes on which clairvoyant vision may be exercised, and the conditions which render its exercise possible.

We are constantly assured in Theosophical literature that all these higher faculties are presently to be the heritage of mankind in general—that the capacity of clairvoyance, for example, lies latent in every one, and that those in whom it already manifests itself are simply in that one particular a little in advance of the rest of us. Now this statement is a true one, and yet it seems quite vague and unreal to the majority of people, simply because they regard such a faculty as something absolutely different from anything they have yet experienced, and feel fairly confident that they themselves, at any rate, are not within measurable distance of its development.

It may help to dispel this sense of unreality if we try to understand that clairvoyance, like so many other things in nature, is mainly a question of vibrations, and is in fact nothing but an extension of powers which we are all using every day of our lives. We are living all the while surrounded by a vast sea of mingled air and ether, the latter inter-penetrating the former, as it does all physical matter; and it is chiefly by means of vibrations in that vast sea of matter that impressions reach us from the outside. This much we all know, but it may perhaps never have occurred to many of us that the number of these vibrations to which we are capable of responding is in reality quite infinitesimal.

Up among the exceedingly rapid vibrations which affect the ether there is a certain small section—a very small section—to which the retina of the human eye is capable of responding, and these particular vibrations produce in us the sensation which we call light. That is to say, we are capable of seeing only those objects from which light of that particular kind can either issue or be reflected.

In exactly the same way the tympanum of the human ear is capable of responding to a certain very small range of comparatively slow vibrations—slow enough to affect the air which surrounds us; and so the only sounds which we can hear are those made by objects which are able to vibrate at some rate within that particular range.

In both cases it is a matter perfectly well known to science that there are large numbers of vibrations both above and below these two sections, and that consequently there is much light that we cannot see, and there are many sounds to which our ears are deaf. In the case of light the action of these higher and lower vibrations is easily perceptible in the effects produced by the actinic rays at one end of the spectrum and the heat rays at the other.

As a matter of fact there exist vibrations of every conceivable degree of rapidity, filling the whole vast space intervening between the slow sound waves and the swift light waves; nor is even that all, for there are undoubtedly vibrations slower than those of sound, and a whole infinity of them which are swifter than those known to us as light. So we begin to understand that the vibrations by which we see and hear are only like two tiny groups of a few strings selected from an enormous harp of practically infinite extent, and when we think how much we have been able to learn and infer from the use of those minute fragments, we see vaguely what possibilities might lie before us if we were enabled to utilize the vast and wonderful whole.

Another fact which needs to be considered in this connection is that different human beings vary considerably, though within relatively narrow limits, in their capacity of response even to the very few vibrations which are within reach of our physical senses. I am not referring to the keenness of sight or of hearing that enables one man to see a fainter object or hear a slighter sound than another; it is not in the least a question of strength of vision, but of extent of susceptibility.

For example, if anyone will take a good bisulphide of carbon prism, and by its means throw a clear spectrum on a sheet of white paper, and then get a number of people to mark upon the paper the extreme limits of the spectrum as it appears to them, he is fairly certain to find that their powers of vision differ appreciably. Some will see the violet extending much farther than the majority do; others will perhaps see rather less violet than most, while gaining a corresponding extension of vision at the red end. Some few there will perhaps be who can see farther than ordinary at both ends, and these will almost certainly be what we call sensitive people—susceptible in fact to a greater range of vibrations than are most men of the present day.