On the other hand, Kant combined these two viewpoints to some extent. Kant believes that knowledge is acquired by human beings through senses and reason. Experience is a necessary condition for knowledge, but it is not the only factor. Transforming experience into knowledge requires rationality (Kant, like Aristotle, called this rationality "category"), and rationality is innate. Human beings gain external experience through the framework of category, and without category, they cannot perceive the world. Therefore, category, like experience, is a necessary condition for acquiring knowledge. However, there are also some factors that can change people's concept of the world. He realized that things themselves are different from what people see, and people can never know the true face of things. In Critique of Pure Reason, Kant pointed out that no one can be similar to an object that exists in a world without time and space, so he emphasized that experience is impossible without time and space, both of which take precedence over everything. In addition, Kant also believes that experience must come from outside the mind. In other words, a person can perceive and understand the world around him, but he can never perceive and understand himself, because the production of knowledge needs three elements: time, space and category.
In the aspect of causality, Kant also overthrew Hume's view. Hume believes that the law of causality does not exist, and human beings only think that there is a connection between the two phenomena because of habit. In other words, we can only perceive the movement of the white ball and the black ball, but we can't perceive the reason why the white ball causes the black ball movement. It is precisely because we can't perceive the law of causality itself that Hume thinks that we can't prove the existence of the law of causality. However, Kant believes that the law of causality is the result of human rationality. Kant agrees with Hume that the law of causality does not come from experience, but he thinks that the law of nature can be proved because it is the law of human cognition. The law of causality is actually the expression of human rationality.
In ethics, Kant denies that will is dominated by external factors, but thinks that will legislates for itself, and human beings' ability to distinguish right from wrong is innate, not acquired. This set of laws of nature is an overwhelming command, applicable to all situations, and a universal moral code. Kant believes that true moral behavior is an act made purely on the basis of obligation, and doing things for personal utilitarian purposes cannot be considered as moral behavior. Therefore, according to Kant, whether an act conforms to the moral norms does not depend on the consequences of the act, but on the motivation of taking the act. Kant also believes that we are free only by obeying moral laws, because we abide by our own moral standards. If we just want to do so, we are not free, because you have become a slave to all kinds of things.