Abstract: Hume discusses human emotions and their occurrence from the natural innate structure of human. For Hume, the sense of happiness and bitterness is the most primitive emotion, which originates from the natural structure of human beings. From the natural structure of human beings and the sense of bitterness and happiness, a series of passions emerge. Human emotions determined by human deep natural structure are the motivation of human actions. Reason is not the motivation of behavior, and it only explores the relationship between cause and result. Reason alone is not enough to produce any behavior. At the same time, reason is the discovery of truth and falsehood. Therefore, rational judgment is not moral judgment, and rationality cannot find out the moral meaning of human behavior. Virtue and vice are the objects of moral emotion. The inner structure of human nature, or moral feeling, makes us distinguish good from evil. In Hume's naturalistic theory of emotions, sympathy, a theory of emotional resonance between people, plays a pivotal role. Hume believes that because of similar or identical structures of human nature, the happiness of others will stimulate our happiness, and the pain of others will cause our pain. However, when he says that the happiness of the rich would cause our happiness, he hardly considers the feeling of the poor. This is the problem of his explanation about sympathy from the natural structure. Besides, Hume focuses on the emotion of mercy, and puts forward the emotion theory of benevolence through the analysis of mercy.

Key words: naturalism, emotion, sympathy, reason