Fear, along with love and anger, is one of the three basic emotions. Like the other emotions, fear affects the way our bodies function. Among other reactions, we breathe faster, our hearts beat faster, and our digestion slows down or stops.
Fear is caused by a threat to our security. We recognize fear as a painful feeling of threatening evil, or trouble, or danger. Sometimes the threat is real, but sometimes it is imagined. When fear and anxiety without cause overwhelm a person, he is said to be emotionally ill.
Fear first occurs in an infant's life when he is physically hurt, when he is too strongly stimulated, or when something unexpected, such as falling, happens to him. Later the child reacts with fear to such situations as hunger, long or unexplained absences of his parents, strange people, and strange animals. Basically we are frightened by that which we know will hurt us, that which stimulates our sense organs too intensely, and that which is too strange for us to comprehend or predict.