We find among sensitive people all degrees of this kind of clairvoyance, from that of the man who gets a vague impression which hardly deserves the name of sight at all, up to the full possession of etheric and astral vision respectively. Perhaps the simplest method will be for us to begin by describing what would be visible in the case of this fuller development of the power, as the cases of its partial possession will then be seen to fall naturally into their places.
Let us take the etheric vision first. This consists simply, as has already been said, in susceptibility to a far larger series of physical vibrations than ordinary, but nevertheless its possession brings into view a good deal to which the majority of the human race still remains blind. Let us consider what changes its acquisition produces in the aspect of familiar objects, animate and inanimate, and then see to what entirely new factors it introduces us. But it must be remembered that what I am about to describe is the result of the full and perfectly-controlled possession of the faculty only, and that most of the instances met with in real life will be likely to fall far short of it in one direction or another.
The most striking change produced in the appearance of inanimate objects by the acquisition of this faculty is that most of them become almost transparent, owing to the difference in wave-length of some of the vibrations to which the man has now become susceptible. He finds himself capable of performing with the utmost ease the proverbial feat of "seeing through a brick wall," for to his newly-acquired vision the brick wall seems to have a consistency no greater than that of a light mist. He therefore sees what is going on in an adjoining room almost as though no intervening wall existed; he can describe with accuracy the contents of a locked box, or read a sealed letter; with a little practice he can find a given passage in a closed book. This last feat, though perfectly easy to astral vision, presents considerable difficulty to one using etheric sight, because of the fact that each page has to be looked at _through_ all those which happen to be superimposed upon it.
It is often asked whether under these circumstances a man sees always with this abnormal sight, or only when he wishes to do so. The answer is that if the faculty is perfectly developed it will be entirely under his control, and he can use that or his more ordinary vision at will. He changes from one to the other as readily and naturally as we now change the focus of our eyes when we look up from our book to follow the motions of some object a mile away. It is, as it were, a focussing of consciousness on the one or the other aspect of what is seen; and though the man would have quite clearly in his view the aspect upon which his attention was for the moment fixed, he would always be vaguely conscious of the other aspect too, just as when we focus our sight upon any object held in our hands we yet vaguely see the opposite wall of the room as a background.