2. The law of mutual change of quality refers to the law of the development of things, from the accumulation of quantity to the leap of quality, telling us to pay attention to the accumulation of quantity at ordinary times. When the equivalent accumulation is certain, it breaks through the limitation of degree and reaches a qualitative leap.
3. The law of negation of negation points out the development process of things. It is a historical necessity for new things to replace old things, but we should "take the essence and discard the dross" when treating old things. The development of things is not achieved overnight, but a spiral process. As the saying goes, "the future is bright and the road is tortuous."