Answer:
As the father of western logic, Aristotle was the first to develop a formal system for reasoning. He observed that the deductive validity of any argument can be determined by its structure rather than its content, for example, in the syllogism: All men are mortal; Socrates is a man; therefore, Socrates is mortal. Even if the content of the argument were changed from being about Socrates to being about someone else, because of its structure, as long as the premises are true, then the conclusion must also be true. Aristotelian logic dominated until the rise of modern propositional logic and predicate logic 2000 years later.