The same law, the law of contradiction, the law of row in the center, the law of reason.

I. Law of contradiction: one of the basic laws of traditional logic. Also known as the law of non-contradiction. It is usually expressed as A is not non-A, or A can not be both B and not B. In traditional logic, the law of contradiction is first put forward as a law of things, meaning that any thing can not have a certain property and not have a certain property at the same time. As a law of thought, it means that no proposition can be true and untrue at the same time. The law of contradiction is also taken as a normative law of cognitive activity, meaning that no one should assert both a proposition (A) and its negation (not A). This means that one should not be ambivalent about a proposition and its negation in order not to contradict oneself. The law of contradiction is also seen as a law of logical semantics, i.e., the same word or statement should not express an idea and not express an idea at the same time in the same context. By violating the law of contradiction, a thought is in logical contradiction (A and not A). And any thought containing logical contradictions is always wrong, so the non-contradiction of thought is an indispensable condition for correct thinking and one of the most important principles of constructing a theoretical system. In modern logic, (A∧A) (read as A and non-A is false), is the embodiment of the law of contradiction in propositional logic; ?x(F(x)∧F(x)) (read as there is not an individual x, and x has the property of F and not the property of F), is the embodiment of the law of contradiction in predicate logic. Second, the law of the center: one of the basic laws of traditional logic. It is usually expressed as A is B or not B. Traditional logic first takes the law of exclusion as a law of things, which means that any thing has a certain property or does not have a certain property at the same time, and there is no other possibility. It is also a law of thought that a proposition is true or not true, and that there is no other possibility. The law of exclusion is also a normative law of cognitive activity, which means that no one should deny both a proposition (A) and its negation (not A), i.e., no one can say two things about a proposition and its negation. The law of neutrality is also taken as a law of logical semantics, which means that any word or statement should either express a certain idea or not express it in the same context. As the latter two laws, it is also called the requirement of the law of neutrality. The law of exclusion does not exclude the fact that there are intermediate stages in the development of a concrete thing, as well as a variety of states and possibilities. In modern logic, A∨A (read: A or non-A), is a manifestation of the law of neutrality in propositional logic, and "x(F(x)∨F(x)) (read: for any individual x, x has property F or not) is a manifestation of the law of neutrality in predicate logic. Since constructive logic does not recognize the existence of real infinity in the real world, but only recognizes infinity as a process, the law of neutrality does not hold in this logic when it comes to infinite objects, and proving the existence of a proposition by contrapositive is not a valid method of proof. Example sentence: It is a violation of the principle of the law of exclusion to say that "this weed is sharp and invulnerable" and to say that "this shield is strong and cannot be pierced". Third, the same law: one of the basic laws of formal logic, that is, in the same thinking process, must be used in the same sense of concepts and judgments, can not be confused with different concepts and judgments. The formula is: "A is A" or "A is equal to A" includes three aspects: (1) the same thinking object. In the same thinking process, the object of thinking must remain the same; in the discussion of the question, answer the question or refute others, all parties to the object of thinking must also remain the same.

(2) The same concept. In the same thinking process, the concepts used must remain the same; in discussing a problem, answering a question or refuting someone else, the concepts used by all parties must also remain the same. (3) The same judgment. The same subject (individual or collective) at the same time (the corresponding objective things in a relatively stable state), from the same side of the same thing to make the same judgment must remain the same. Homogeneity requires the certainty of thinking, but it does not deny the development of thinking. It speaks of the process of thinking, and does not require the object to remain the same, absolutely unchanged. Logic of the "same law" aspect of the content, should include "the same position" and "the same space-time" in it. The Law of Sufficient Reason: Logicians who claim that the law of sufficient reason is also one of the basic laws of traditional logic usually express this law as follows: any judgment must be (sufficiently) justified. The Law of Sufficient Reason originated from the German philosopher Leibniz, G.W., in the late 17th and early 18th centuries. In his Monadology, he said: "Our reasoning is founded on two great principles, namely: (1) the principle of contradiction, ...... (2) the principle of sufficient reason, by virtue of which we hold that, if any thing be true, or real, and if any statement be true, there must be a reason why this and not that is the case. There must be a good reason why it is so and why it is not so, though these reasons are often not always known to us". However, Leibniz himself did not take the principle of sufficient reason as a law of logic. What exactly he meant by the principle of sufficient reason has also been a matter of debate. According to Kant, I., both the law of contradiction and the law of sufficient reason are logical or formal criteria of truth. In his view, the law of contradiction is a negative criterion, since a thought that obeys the law of contradiction is not necessarily true, and a thought that violates the law of contradiction cannot be true; while the law of sufficient reason is a positive criterion, since a thought that obeys the law of sufficient reason is necessarily well-founded, and is a thought that follows from some principle and does not lead to a false conclusion. But traditional logicians have generally held that the law of sufficient reason is not so much a law about the form of thought and formal logic as it is a law about existence and facts. For this reason, this law is not stated in many traditional logical works, and it is not discussed in modern logic.