When Craig orders her mind, or some portion of it, or faculty of it, to get what is in Bob’s mind, while Bob is forty miles away—and when her mind does that, what are we to picture as happening? If I am correct in my guess, that mind and body are two aspects of one reality, then we shall find some physical form of energy being manifested, just as we do when we communicate by sound waves. The human brain is a storage battery, capable of sending impulses over the nerves. Why may it not be capable of sending impulses by means of some other medium, known or unknown? Why may there not be such a thing as brain radio? Certainly we know this, that every particle of energy in the universe affects to some slight extent every other particle. The problem of detecting such energy is merely one of getting a sufficiently sensitive device. Who can say that our thoughts are not causing vibrations? Who can set a limit to the distance they may travel, or to the receiving powers of another brain, in some way or other attuned thereto? Any truly scientific person will admit that this is a possibility, and that it is purely a question of experimenting, to find out if it does happen, and how. Again, consider the problem of clairvoyance, suggested by Craig’s ability to tell what is inside a book she holds in her hand without seeing it, or to reproduce drawings when no human mind knows what drawing she holds. How are we to figure that as happening? Shall we say that brain vibrations affect material things such as paper, and leave impressions which endure for a long time, possibly forever? Can these affect another brain, as in the case of a bit of radium giving off emanations? It seems to me correct to say that, theoretically, it is inevitable. Every particle of energy that has ever been manifested in the universe goes on producing its effects somewhere, somehow, and the universe is forever different because of that happening. The soil of Britain is still shaking with the tramp of Caesar’s legions, two thousand years old. Who can say that some day we may not have instruments sensitive enough to detect such traces of energy? On the very day that I am reading the galley proofs of this book, I find in my morning paper an Associated Press dispatch, from which I clip a few paragraphs. “A fundamental discovery in photography that takes the ‘pictures’ directly on cold, hard untreated metal without the usual photographer’s medium of a sensitized plate was made public tonight at Cornell University. It reveals that seemingly impervious metal records on its surface unseen impressions from streams of electrons and that these marks can be brought into visibility by the right kind of a ‘developer,’ exactly as photographic images are brought out on sensitized paper....