To take the simplest example: one man laughs, and another, who hears, becomes merry; or a man weeps, and another, who hears, feels sorrow. A man is excited or irritated, and another man, seeing him, comes to a similar state of mind. By his movements, or by the sounds of his voice, a man expresses courage and determination, or sadness and calmness, and this state of mind passes on to others. A man suffers, expressing his sufferings by groans and spasms, and this suffering transmits itself to other people; a man expresses his feeling of admiration, devotion, fear, respect, or love to certain objects, persons, or phenomena, and others are infected by the same feelings of admiration, devotion, fear, respect, or love to the same objects, persons, and phenomena.