Sometimes the thoughts and conditions of mind of another person make so strong an impression upon us, either in the presence of that person or in his absence, according to the extent of his power, that his condition is transferred to us. We sometimes laugh without reason on seeing the intensity of another person's laughter, and we feel sad without any reason when we are in contact with one who is sorrowful. We fulfil the wish of another, not knowing that he had any such wish, sometimes even without his own knowledge of it.