The relations of the objective world are complex, some of which conform to the rules of formal logic and some of which do not. These relationships are objective and real, but because they are very complex, we can not accurately understand them, can not carry out logical deduction and prediction, and can not get the conclusions we want. If you want to carry out logical deduction and prediction, you must simplify these real relationships, and then you can conclude, calculate, statistics and predict the phenomena of observation, measurement and testing, so that there is formal logic. So the characteristic of formal logic is simple and useful but not objectively true. This is an important theorem.

Theorem: Formal logic is simple and useful rules that are not objectively true.

Almost all the reasoning of science and technology uses formal logic, so all the conclusions of science and technology are not absolutely objective and accurate. We often fail because of using these conclusions in practice, but with the development of science and technology, the success rate will gradually increase. If formal logic is objective and true, then science and technology should be able to guarantee our practical success, but science and technology can never guarantee our success, only let us constantly improve the success rate.

Making objective things conform to formal logic is a completely artificial rule. Because only by following these rules can we derive useful conclusions. We need to use the law of identity, the law of exclusion of middle, and the law of non-contradiction every day, and deduce many simple and useful but untrue conclusions with formal logic every day. Because we use it every day and get used to it, we don't pay attention to it, we don't seem to have made any simplification, and it seems that all the reasoning is objective, true and accurate. The main task of philosophers is to discover these neglected things.

The simplification of complex content has long become our mindset, a priori thing, as if this mindset does not need testing. The priori means that there is no need for testing. Many people think that formal logic must be correct, a priori ability to acquire knowledge, this view is wrong, and any product of thought needs to be tested in practice to see if it is really valuable. The process of simplifying what is real and concrete is not that our understanding conforms to the objective world, but that the objective world conforms to our understanding. This is what Kant called the Copernican Revolution. But Kant did not explain the nature of formal logic with this revolution theory.

Pavlov-trained dog thought of food when it heard a bell, it thought yesterday's bell was the same as today's bell, and it didn't know that the bell that sounds the same might come from a different person, or the same person for a different purpose. If the bell is set to A, the animal will think that A always equals A. If this kind of thinking can make it eat enough every day, then it thinks it is the truth.

Man came from animals, and man's thinking came from animals' thinking. The way of thinking of animals is conditioned reflex, and the basic type of human thinking (the instinctive form of thinking) is also conditioned reflex. Since formal logic could solve most problems in life, this kind of conditioned reflex was reinforced and became a fixed thinking of people. Later, people found that some things did not conform to formal logic, and this way of thinking had to be modified, so dialectical logic was born. Objective relations contain contradictions. But formal logic is useful, it can reason, it can draw useful conclusions, so formal logic seems objective.