1 and "contradiction" are divided into logical contradiction and dialectical contradiction. These are two fundamentally different concepts.

2. Saying that "contradiction is the mismatch between preface and postscript" is a violation of the law of contradiction in formal logic. The "contradiction" here refers to the contradiction in formal logic.

3. Dialectical contradiction, that is, philosophical contradiction, refers to the contradictory and unified relationship contained in the thing itself. In short, contradiction is the unity of opposites.