These characteristics of practice enable people to compare subjective knowledge with objective objects and their laws through the results of practice, and judge whether subjective knowledge is consistent with objects, that is, to prove the truth of knowledge. If people's practical activities under the guidance of certain subjective knowledge achieve the expected results, it proves that this subjective knowledge is in line with the objective reality and has truth; On the contrary, this subjective understanding does not conform to the objective reality and is a fallacy. Practice tests and verifies the truth of knowledge in three forms: practice creates new objects in order to make people realize their knowledge in objects; Change the real facts (including the attribute of things and the relationship between things) through practice to achieve the expected purpose of people; Through practice, the objective things can be used and controlled. As the standard of cognitive truth, practical test is the unity of opposites between certainty and uncertainty: the truth of knowledge can only be tested by social practice, and practice will eventually prove the truth of knowledge, which is its certainty; The concrete social practice always has historical limitations. It can not fully confirm or refute all existing knowledge, but can only test the truth of knowledge relatively correctly, which is its uncertainty. This unity of certainty and uncertainty not only makes people draw a clear line with all forms of idealism and agnosticism, but also makes people not absolutely rigid existing knowledge. [1]
