When I find a book that teaches a boy good business habits and helps him to become a good business man, I know that book was written with that object in view. When I find a book that teaches one how to understand the human system, the nature of disease and the character of the remedies which are to be used when people are sick, I know that book was written with a view to help people to understand the nature of disease and the character of medicine. Just so it is with every other book. Each is like the lock and the key, for the locks have inside a peculiar sort of winding way, and when I find a key that exactly fits into this winding passage I know immediately that the locksmith designed that the key should fit into that particular lock and turn back the bolt. Now, God wants to get into the human heart, and I find that God has a key with which to unlock it. I do not think you would be long in guessing what book God has made the key with which to unlock the human heart. I think that every boy and girl would at once say that it is the Bible. Yes; it is the Bible. It fits exactly into all the wards and chambers, and winding passages which characterize each and every need of the human heart. The moment I bring this wonderful key of divine truth to the human heart, I find that the lock and the key were both made by the same infinite Creator. Some locks are very complicated and intricate, and the keys are also very peculiar. They are made especially for that particular lock, and no other key in all the world will unlock it. The moment I get that particular key and turn it around in the lock I know at once that both the lock and the key were made by the same person, and that the lock was made to be opened by no other key. So God has created the human heart and made it very difficult to be opened, and there is no key in all the world that can open it except the Bible. As a robber or a burglar may try to get into a house by the use of a skeleton key, or by "picking the lock," so men have often tried to gain admission into the human heart by the use of various substitutes for the genuine and the real key. They have tried amusement, and wealth, and sinful pleasure, and very, very many things; but they never succeed in getting into the inner sacredness of the human heart. Unless the heart is opened by God's Word, and the Holy Spirit is admitted so that God can take possession, there is always a sense of loneliness, a sense of dissatisfaction, a desire for something that the person does not possess; he is at unrest, he is restless and dissatisfied, like a boy or girl who is away from home, and has a homesick longing to return to that home.