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How did Aristotle distinguish two meanings of possible?
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Ancient logic
Zeno's paradox, illustrated by Achilles' racing a tortoise.
In his study of modal logic, Aristotle distinguished between two specific meanings of the term "possible":12
- Sense 1: That which is not impossible, defined as the opposite of which is not necessary.12
- Sense 2: That which is neither necessary nor impossible, also known as the contingent.12
In the context of his modal syllogistic, Aristotle consistently utilized the second senseāthe contingentāwhen constructing premises. However, he occasionally employed the first sense in his conclusions, particularly when a conclusion derived using the second sense would be logically incorrect.12