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How did Aristotle influence the formal study of correct reasoning?
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Plato (center left) and Aristotle, detail from School of Athens, fresco by Raphael, 1508–11; in the Stanza della Segnatura, the Vatican. Plato is shown pointing to the heavens and the realm of forms, Aristotle to the earth and the realm of things.
Aristotle is widely credited as the founder of the systematic study of logic. He established a rigorous framework for reasoning, primarily through his collection of six works known as the Organon, which he viewed as a universal tool for all sciences rather than a theoretical science itself.123
His influence on the formal study of correct reasoning includes several key innovations:
- Use of Variables: Aristotle was the first logician to use schematic letters (variables) as placeholders for terms. This allowed him to achieve a level of abstraction and generality essential for analyzing the structure of arguments.123
- Syllogistic Theory: In his Prior Analytics, he developed the theory of the syllogism, a method of inference where a conclusion is drawn from two premises. He identified specific "moods" of syllogisms and established rules to determine which forms result in valid inferences.13
- Term Logic: His system focused on the logical relations between terms (subjects and predicates) within propositions, categorizing them by quantity (universal vs. particular) and quality (affirmative vs. negative).123
- Fallacy Analysis: In his Sophistic Refutations, he provided a foundational discussion of various logical fallacies.12