If, as many believe, the next great strides of science are to be in this direction, it may pay some of us to be pioneers in learning how to make use of these undeveloped riches of memory, organization, and surplus energy. The subconscious, which can on occasion behave like a very devil within us, is, when rightly used, our greatest asset, the source of powers whose appearance in the occasional individual has been considered almost superhuman, but which prove to be characteristically human, the common inheritance of the race of man. CHAPTER VI _In which we learn why it pays to be cheerful_ BODY AND MIND THE MISSING LINK =Ancient Knowledge.= People have always known that mind in some strange way carries its moods over into the body. The writer of the Book of Proverbs tells us, from that far-off day, that "A merry heart doeth good like a medicine, but a broken spirit drieth the bones." Jesus in His healing ministry always emphasized the place of faith in the cure of the body. "Thy faith hath made thee whole," is a frequent word on His lips, and ever since His day people have been rediscovering the truth that faith, even in the absence of a worthy object, does often make whole. Faith in the doctor, the medicine, the charm, the mineral waters, the shrine, and in the good God, has brought health to many thousands of sufferers. People have always reckoned on this bodily result from a mental state. They have intuitively known better than to tell a sick person that he is looking worse, but they have not always known why. They have known that a fit of anger is apt to bring on a headache, but they have not stopped to look for the reason, or if they have, they have often gotten themselves into a tangle. This is because there has always been, until recently, a missing link. Now the link has been found. After the last chapter, it will not be hard to understand that this connecting link, this go-between of body and mind, is nothing else than the subconscious mind. When we remember that it has the double power of knowing our thoughts and of controlling our bodies, it is not hard to see how an idea can translate itself into a pain, nor to realize with new vividness the truth of the statement that healthy mental states make for health, and unhealthy mental states for illness.