The trouble is that fear has a great tendency to function to excess, especially in the years of childhood, that formative period which means so much to future development. There is scarcely one of us who, looking back, cannot recall some youthful fear, abnormal in its intensity. Nor are such abnormal fears confined to the young. With many people they persist in one form or another throughout life; it may be as fear of thunder, fear of mice, fear of snakes. Moreover, they sometimes do not appear with full force until the period of youth is long past. At the age of thirty or forty—at any age—there may develop, with irresistible power, and seemingly for no reason, a paralysing, appalling fear of doing some trivial, everyday act, or of coming into contact with some familiar and entirely harmless object. When fear becomes as extreme as this it amounts to a disease, and is recognised as such by the medical profession, being technically known as a “phobia.” It is through scientific study of these phobias, as recently carried out by medical specialists with a psychological training, that full realisation has been gained of the tremendous rôle played by fear in the life of man, and the need for its proper control and direction. The two commonest phobias are direct opposites of one another—namely, fear of open places (agoraphobia) and fear of being in a closed place (claustrophobia). The victim of agoraphobia can with difficulty be persuaded to trust himself outdoors. He fears that if he goes out some catastrophe will overwhelm him. His state of mind is one of absolute panic, and when obliged to cross any open space, such as a public park, he displays all the symptoms of extreme fear. The person troubled with abnormal fear of closed places experiences no difficulty of this sort. He is, on the contrary, never so happy as when in the open. His troubles begin when he is asked to take, say, a drive in a cab or a journey in a railway car. He dare not attend the theatre, or any indoor public entertainment. Whence comes his aversion from closed places he cannot say. He only knows that the mere thought of being in any place from which he cannot escape at a moment’s notice fills him with a torturing dread.