Combining Philosophers

Ideas for Hermarchus, Sarah Bakewell and Aristotle

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2 ideas

5. Theory of Logic / A. Overview of Logic / 6. Classical Logic

12376	Demonstrations by reductio assume excluded middle [Aristotle]
	Full Idea: Demonstrations by reduction to the impossible assume that everything is asserted or denied.
	From: Aristotle (Posterior Analytics [c.327 BCE], 77a23)
	A reaction: This sounds like the lynchpin of classical logic.

5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic

11033	Predications of predicates are predications of their subjects [Aristotle]
	Full Idea: Whenever one thing is predicated of another as of a subject, all things said of what is predicated will be said of the subject also.
	From: Aristotle (Categories [c.331 BCE], 01b10)