These difficulties are much reduced, though not entirely removed, if we suppose that the agent is embodied, not in the four-dimensional vehicle, but in what, for lack of a better word, is called the "Etheric Double." This appears to be of a semi-material nature and is discussed at length in the chapter dealing with "The Connecting Link."
But this supposition would involve special difficulties of its own.
There is reason to suppose that the "Etheric Double," if it exists at all, is incapable of moving far from the physical body during life and it does not appear well adapted for use as a vehicle after death.
But on this point I shall have more to say later.
Generally speaking, it seems probable that no one of these explanations will be found to cover all the cases in question. But each is likely to prove applicable to some of them, although much careful investigation and analysis will be necessary before we can hope to be able to allot each case to its true cause with any degree of assurance.
None the less I am convinced that the hypothesis of a four-dimensional vehicle, detachable on occasion from the physical body, puts us, at least, on the right track.
I will now turn to the consideration of a series of phenomena which, from the point of view of the higher space hypothesis, are of far greater interest and significance than any we have yet considered.
I refer to the phenomena of "apport" and of "apparent penetration of matter by matter."
If we have a closed room, of which all the windows, doors, and other apertures have been carefully shut and sealed, it is clearly impossible to introduce any solid object into that room, by normal means, without breaking the seals and opening one of the apertures. The same would apply to a closed, locked and sealed box.