Suppose that "A" Fig. 7, represents a two-dimensional observer and that X, Y, and Z are two-dimensional closed spaces, rooms, houses, or what not. The interiors of these closed spaces will be invisible to "A." All he will be able to see will be a straight line as at "B," for the boundaries of X, Y, and Z will be opaque and impassable to him. But now suppose that he were to be lifted up vertically, out of the plane of the paper altogether. He would from this new position be able to see the interiors of X, Y, and Z, together with any two space incidents occurring therein. They would present approximately the appearance shown in Fig. 7 and the degree of foreshortening would diminish with the height to which he ascended above the plane of the paper. In a precisely analogous manner we must suppose that three-dimensional obstructions do not exist for, and that the interiors of closed three-dimensional spaces are entirely open to, anyone who could regard them from a point situated in four space, _i.e._, removed from three space to a suitable distance in the direction of the fourth dimension. The greater this distance the less will be the foreshortening and the greater will be the range of vision. There would be no question of intervening objects obscuring the view, simply because, in four space, three space objects do not intervene--the view of X in Fig. 7 is in no way obscured by the presence of Y or Z. Compare with this the statements of many clairvoyants to the effect that when in the clairvoyant state they can, and do, see the front, sides, back, and every internal point of three space objects simultaneously. The parallel is almost irresistible in its significance. Compare also the following case given by Professor de Morgan, and which is typical of the very numerous cases of this nature on record. In this case the percipient was a little girl who was undergoing mesmeric treatment for fits by Mrs. de Morgan. While in the mesmeric state she was desired to follow Professor de Morgan mentally to the house at which he was dining and which was totally unknown to the child. The girl got there at once and gave an accurate description of the room in which the Professor was, the furniture which it contained, the people to whom he was talking and various small incidents which took place. On his return Professor de Morgan confirmed every detail of the description. This is, of course, a very condensed resumé of the occurrence. Interested readers should consult contemporary Psychic literature which abounds with such cases. The point is that no amount of retinal hypersensibility will so much as begin to explain this sort of case, whereas it is not so utterly incomprehensible when we introduce the idea that the percipient may have been seeing four-dimensionally. It is hardly necessary to observe that the sense organs involved cannot be the physical eyes. They must be supposed to belong to the four dimensional vehicle.