Deduction
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It’s almost time to reveal what is, in my opinion, the single greatest diagram in western philosophy. But before we can do that, we have to learn about subalternate propositions.
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Here we get to the heart of traditional logic: the ability to learn what we don’t know from things we already do know, even things we know to be false. We do this through propositions of equivalence and opposition.
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For centuries, logicians have understood that even very simple acts of reasoning have three distinct dimensions. To understand the science of sound reasoning, we need to appreciate the marvelous (though hidden) complexity of our thought processes.
Logic Lectures 