Article 4 of China's General Principles of Civil Law stipulates that "civil activities should follow the principles of voluntariness, fairness, equal compensation and good faith", thus making China the first socialist country to write the principle of good faith into law. The significance of this move is manifold. According to this highly applicable principle, it gives judges certain discretion to meet the needs of coordinating various complex and changeable social contradictions and adjusting various social and economic relations.

1, the connotation of the principle of good faith and its basis as the principle of civil law.

The principle of good faith mentioned in the general principles of civil law is originally a long-standing moral norm in human society. It has two basic meanings: honesty means that words and deeds are true, in line with the situation, without falsehood and fraud; Credit refers to observing the rules of agreement or commitment, and fulfilling and undertaking the obligations determined by the rules of agreement or commitment. These two meanings are independent and related. Credit originates from honesty, and honesty is found in credit. The combination, mutual support and mutual tolerance of the two have become universal moral principles in interpersonal communication. This universal applicability of the principle of good faith is based on its generality and abstraction, so its connotation and extension are uncertain. But this does not prevent it from playing a role as a universal moral norm. With the development of society and the progress of the times, the scope of application of the principle of good faith has gradually expanded, from simple interpersonal relationships and social ethics to socio-economic and political activities, and its connotation and extension are also constantly developing. It is far from meeting the needs of society to play a role only as a moral code. This is because:

(1) The society needs to raise the moral standards of economic activities to mandatory legal norms.

Since ancient times, people have always been consciously or unconsciously restricted or influenced by certain moral consciousness in economic activities. As the most common moral principle, honesty will naturally restrict and influence people's economic activities. However, this constraint and influence is based on the self-discipline or habitual atmosphere of the parties, not external coercion. Therefore, the ugly behavior of treachery, deception and fraud in order to obtain ill-gotten wealth in economic activities is not enough to constitute a strong constraint. This also shows that simple moral constraints can not guarantee the honesty and credibility of people's behavior and the fairness and justice of society. In this context, it has become an objective need of society to raise some universal moral standards to mandatory legal norms that everyone must abide by. It is a logical result of adapting to the needs of society to list honesty and credit as a principle clause of civil law.

(2) It is the need to overcome the lag of written law.

Social life is constantly developing and changing, and new situations and problems are always emerging. No matter how complete and comprehensive the written law is, it will inevitably lag behind compared with the ever-changing social life. This shows that the existing legal provisions are often in a difficult position when they are applied to complex and diverse cases. The best way to get out of this dilemma is: on the premise of not losing social fairness and justice, legislation gives judicial organs certain discretion on the basis of existing statutory provisions. Taking honesty and credit, a moral norm with universal significance, as the general guiding principle of civil law provides a legal norm for the implementation of civil law provisions to realize social fairness and justice. When the existing legal provisions are not fully applicable to the case, the judge can have certain discretion to implement this guiding principle, so as to ensure that the result of the ruling can meet the purpose of social fairness and justice. Here, the principle of good faith is not only the legal basis for the necessary extension and expansion of statute law, but also the reasonable boundary for this extension and expansion. In the judicial process of implementing the principle of good faith, we should combine overcoming the lag of written law with maintaining the authority of law and excluding the arbitrariness of justice.

2. The role of the principle of good faith in civil law.

First of all, guide the parties to engage in civil activities correctly. As a widely applicable civil code of conduct, the principle of good faith clearly warns the parties what behavior is protected by law and what behavior is not allowed by law; How the parties should correctly exercise their rights and perform their obligations without harming the legitimate rights and interests of others and social public interests plays a guiding and normative role in how the parties engage in civil activities.

Second, explain, evaluate and supplement the role of legal acts. As a basic guiding principle of civil law, the principle of good faith can judge and judge the legal acts of the parties, determine their legal effect and legal responsibility, thus supplementing and perfecting the existing legal acts and making them more in line with social justice and fairness.

Third, the role of interpreting and amending laws. Generally speaking, legal provisions are abstract to some extent, and some detailed and targeted explanations are needed when they are applied to specific cases. Interpreting the law under the guidance of the principle of good faith is helpful to maintain the fairness and justice of the law. This is the function of the principle of good faith in legal interpretation. As mentioned above, due to the contradiction between the lag of existing laws and the variability of social development, it is sometimes difficult to accurately judge the application of laws. Based on the principle of good faith, the unsatisfactory parts of the law can be reasonably modified and supplemented, so that the interests and responsibilities of the parties can be fairly distributed, thus realizing the justice and fairness of the law.

Fourth, it plays an auxiliary qualitative role in difficult cases. The characterization of a case is the premise of applying the law. In real life, the nature of some cases is vague and secret, so it is difficult to make an accurate legal judgment for a while. Using the principle of good faith to analyze the facts of these cases will help to develop the truth, goodness and evil of the cases, and will play an important role in correctly judging the nature of the cases, applying the law and distributing the rights and obligations of the parties reasonably and fairly.

Fifth, the role of making up for legal loopholes. Compared with the ever-changing social life, there are inevitably loopholes in the existing written law. Where there are no provisions in the law, it can be made up according to the requirements of the principle of good faith in order to properly handle specific cases. This is the manifestation of the judicial organs making laws. The remedy of legal loopholes provides the basis and conditions for future legislation and revision, which is of great significance to the perfection of legislation.

Sixth, the pursuit of personal justice and social justice. Laws cannot exhaust all aspects of a rapidly changing society. In judicial activities, applying general written provisions to various situations may lead to unfair judgment of individual cases. Here, according to the principle of good faith in the modern sense. Under the condition of socialist market economy, on the one hand, it can guide market subjects to exercise their rights and fulfill their obligations honestly, and shape the integrity spirit of market subjects; On the other hand, by giving the judicial organs the right to interpret, supplement and amend the law freely, we can make up for some shortcomings of the existing law, accumulate experience and create favorable conditions for the further improvement of the legal system in the future.

To sum up, the principle of good faith is a very valuable guiding principle of civil law. Under the condition of socialist market economy, on the one hand, it can guide market subjects to exercise their rights and fulfill their obligations honestly, and shape the integrity spirit of market subjects; On the other hand, by endowing judicial organs with certain discretion to interpret, supplement and amend laws, we can make up for some shortcomings of existing laws, accumulate economy and create favorable conditions for further improvement of the legal system in the future.

3. Applicable conditions of the principle of good faith

The function of the principle of good faith shows that its function depends on the existing legal acts and legal provisions. Guided by this principle, or consider the specific interests of both parties fairly and make a fair conclusion; If the law is unclear, it can be diagnosed and explained; Or make up for loopholes; Or expand a specific obligation to safeguard the legitimate rights and interests of both parties, and so on. Its fundamental purpose is to realize the fairness and justice of law.

In short, it is not only an important subject in the implementation of civil law, but also an important standard to test the level of judicial execution to correctly apply the principle of good faith and give full play to its positive role without abusing it.