“同情”是沟通“他人”和“自我”的核心概念，是休谟伦理学理论的前提性预设。同情作为一种认知机制，沟通着自我与他人的情感。同情发生的过程，是他人情感对自我情感的传导过程，也是自我情感向他人的情感的转化过程。在休谟看来，没有同情、情绪的传导，个人的情感不会受到他人的影响，道德行为就没有产生的动机。同情，即自我对他人印象与观念的感知、联想与想象，是仁爱的情感产生的前提条件。虽然说仁爱的情感与生俱来，但因同情而得以传递的苦乐感在仁爱之情生发过程中是极为重要的诱因。从这个意义上来讲，感知他人的痛苦是仁爱情感产生的必要条件，正是因为人们能感知到他人的痛苦，所以人才会有帮助他人免除痛苦的情感动机与行为。此外，没有同情，不同人、不同社会群体之间的道德判断也没有达成一致的可能。行为的规范、道德的认同，一定离不开自我对他人情感的理解，以及他人情感对自我价值体系的影响。 自我和他人的情感之所以能够达成传递，很大程度上依赖于社会意识对自我意识的长期建构，这种建构通常发生于儿童早期教育和行为培养中。而随着交往范围的扩大、交往领域的拓展、交往对象的变迁，新的社会意识影响下所产生的新的价值信念对旧有的自我意识、价值信念造成冲击，我们的道德情感就会通过反思形成新的反思性平衡，以此来适应新的交往关系。也就是说，人类社会的互动、以及在互动中情感的传递和理解，是塑造心理现象的首要前提。休谟所强调的以同情为基础的“自我反思”，不是对纯粹理性的反诘，而是自我在社会互动中不断想象、体验、认知、修正道德情感的过程。通过对同情的研究，我们可以进一步探求人类情感认同的发生机制、发生前提，以及自我情感和社会情感相互塑造的复杂过程。这种主体间的情感认同，替代纯粹理性、普遍法则，解释了为何在相似的社会环境中，不同人的道德情感反思、道德判断具有相似性。 然而，所有道德相对主义者都会面临一个问题：如何证明道德判断的更替是朝向终极善有序的层进，而不是没有秩序的变化、甚至恶化。休谟采用自然实在论理解人性，用描述的方法解释道德心理，这种理论前提从根本上限制了他提出终极道德指向的可能。但我们也应认识到，提出某种终极的道德指向并非休谟的理论旨趣，休谟的任务在于根据人类的道德苦乐感发现并扩展一些基本的道德原则。也就是说，虽然休谟提出的反思的平衡很难跳出习俗和同情机制本身，但是有些基本的道德判断会在文化的演变中存续下来。这些基本的道德判断逐渐成为普遍原则，成为价值判断的一般标准。休谟伦理学的基本目标是立足于人类心灵活动，提取出道德标准，用以评价以法律为本的政治实践。

Sympathy is the presupposition of Hume's theory. It serves as a cognitive mechanism to communicate self and other people's emotions. Sympathy is the core concept, explaining the process of communicating between others and the self. Without sympathy, the individual’s feelings cannot influence by others. The perception, association and imagination of self-images and ideas of others are prerequisites for the production of benevolence emotions. Although the emotion of benevolence is born to have, but the bitterness and joy conveyed by sympathy is an extremely important cause in the process of the development of benevolence. In this sense, perceiving the pain of others is a necessary condition for the generation of benevolent emotions. It is precisely because people can perceive the pain of others. Therefore, people can have emotional motivations and actions that help others to relieve pain. Also, without emotional transmission, there is no motive for the moral behavior. And moral judgments from different groups of people cannot reach consensus. The normative and ethical identification of behavior closely related to the individual’s understanding of the emotions of others and the influence of others' emotions on the self-value system. Sympathy is the one-way conduction process in which the emotions of others become self-emotions. The reason that the self and other people's emotions can reach the transmission depends largely on the long-term construction of self-awareness by social consciousness. Such construction usually occurs in early childhood education and behavior training. With the expansion of the scope of interaction, the expansion of the field of communication, and the changes in the objects of communication, the values and beliefs under the influence of the new social consciousness will have an impact on the old self-consciousness and value belief, and our moral emotions will form new ones through reflection. Through the study of sympathy, we can further explore the mechanism of the occurrence of human emotional identity, the premise of its occurrence, and the complex process in which self-emotions and social emotions shape each other. Hume's empathy-based "self-reflection" does not means the self-examination by pure reason, but a process in which the self constantly imagines, experiences, recognizes, and corrects moral emotions in social interaction. The interaction of human society and the transmission and understanding of emotions in interaction are the primary prerequisites for shaping the psychological phenomenon. This kind of intersubjective emotional identity, instead of pure reason and universal law, explains the similarity and stability of moral emotion reflection and moral judgment in a certain social environment. However, just as all relativists will face. How to prove that the replacement of moral judgments is towards the ultimate good and would be changing with the order, rather than being changed to the worse has remained a question waiting to answer. Hume uses Natural-realism Theory to understand human nature and use descriptive methods to explain moral psychology. This theoretical premise fundamentally limits his potential for pointing towards ultimate morality. Fortunately, it is not Hume's theoretical purport to point out that moral orientation is the goal. Hume's task is to discover and expand some basic moral principles based on the ethical bitterness of human beings. Although the balance of reflection is actually difficult to break out of the custom and sympathy mechanism itself, some very basic moral judgments on which People reached a consensus would survive the change and evolution of culture. These basic moral judgments gradually become universal principles and become the general standard of value judgment. In other words, Hume's task for himself is not to provide a possible moral world. His moral theory ultimately serves his political thoughts. The basic goal of his ethics is to establish a moral standard based on human spiritual activities to evaluate legally-based political practices.