(1) Deductive reasoning is from general to special reasoning;
(2) It is the inference of the premise implication conclusion;
(3) It is the inference that the premise and conclusion are necessarily related.
(4) Deductive reasoning is an inevitable reasoning with sufficient or necessary conditions between premise and conclusion.
The logical form of deductive reasoning is of great significance to rationality because it plays an irreplaceable role in correcting the rigor and consistency of human thinking. This is because deductive reasoning ensures the validity of reasoning not because of its content, but because of its form. The most typical and important application of deductive reasoning usually exists in logic and mathematical proof.
Deductive reasoning is strict logical reasoning, which is generally manifested as a syllogism model of major premise, minor premise and conclusion: that is, a new judgment is drawn from two judgments that reflect the connection and relationship of objects in the objective world. For example, "all substances in nature are separable, and elementary particles are natural substances, so elementary particles are separable." The basic requirements of deductive reasoning are: first, the judgment of major and minor premises must be true; Second, the reasoning process must conform to the correct logical form and rules. The correctness of deductive reasoning first depends on the correctness of the major premise. If the premise is wrong, the conclusion will naturally not be correct.
Deductive reasoning has syllogism, hypothetical reasoning, selective reasoning, relational reasoning and other forms.
syllogism
It is a deductive reasoning based on two identical property judgments, and a new property judgment is obtained. Syllogism is a general model of deductive reasoning, which consists of three parts: major premise-known general principle, minor premise-special situation of research, conclusion-judging special situation according to general principle.
Hypothetical reasoning of affirming the antecedent
It is reasoning based on hypothetical judgment. Hypothetical reasoning can be divided into sufficient conditional hypothetical reasoning and necessary conditional hypothetical reasoning.
Selective reasoning
It is reasoning based on the judgment of word selection. Selective reasoning can be divided into compatible selective reasoning and incompatible selective reasoning.
Relational reasoning
Relational reasoning is the reasoning in which at least one premise is relational proposition.