Kant believes that the fundamental moral principles of our society come from the rationality of people, and that people must follow these principles unconditionally. These moral principles are the categorical imperative. Meanwhile, its common rules have different directions in society. To conclude these orientations, we can reflect on three different formulations. Among the three formulations, the first formulation of universal law presents remarkable characteristics in the maxim and the constraints on people's behaviors. With a combined analysis of examples, the disadvantages of universal law also appear. To evaluate and explain in order to prove the flaws of universal law, the specific understanding of the meaning of the maxim is essential because it is at the heart of universal law. Maxim is the subjective principle and rule of people. People's actions are based on these principles. Furthermore, the maxim generally refers to a criterion of individual behavior for rational beings. If the principle or maxim that determines people's will cannot be widely effective for rational beings, that maxim of will is only applicable for a specific individual. In this way, this subjective principle is not a moral rule, but arises from personal preferences. Meanwhile, although the maxim is the subjective principle, it should become an objective and universal principle according to the categorical imperative. Universal law prescribes that the maxim is an objective and universal principle. If the maxim is considered as a subjective principle, it will not be applicable to moral life. This would violate the sense of moral value, because not all subjective maxims arise from a sense of duty. Maxim must correspond to the universal principle. Only in this way could the maxim become the central unit of the paper between the content and the forms of philosophy. Usually, the content decides the forms of expression. However, the categorical imperative uses its form to take the form of moral duties. This method is really difficult for people to understand philosophy better. My Chinese teacher once told me that metaphysics is about discovering the wrong reasons for what we instinctively believe. Maybe he's right. Works Cited Kant, Immanuel. “The foundations of ethics”. Moral philosophy, a fourth edition for the reader. Ed. Pojman, Louis P. and Tramel, Peter. Indianapolis/Cambridge: Hackett Publishing Company, Inc, 2009. 218-237. Print.Bergeron, Melissa and Tramel, Peter. “Rightness as fairness: Kant’s categorical imperative.” » Moral philosophy, a fourth edition for the reader. Ed. Pojman, Louis P. and Tramel, Peter. Indianapolis/Cambridge: Hackett Publishing Company, Inc, 2009.238-260.Print.