Within Reason #118 Joe Folley - Everything You Need to Know About Logic
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Aug 24, 2025 
Joe Folley, a Cambridge philosophy graduate and creator of Unsolicited Advice, dives deep into the world of logic. He compares Aristotelian and Stoic logic, revealing how these foundations impact clarity in reasoning. The discussion also touches on the importance of validity versus soundness in arguments and the intriguing consequences of contradictions. Folley simplifies complex concepts like fuzzy and modal logic, while humorously exploring truth claims—like whether your mum knows about your orientation—making the exploration of logic both enlightening and entertaining.
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Logic Governs Truth-Apt Relations
- Logic applies to relations between truth-apt expressions like propositions and predicates.
- Its core role is to show what conclusions truthfully follow from given premises.
Validity Versus Soundness Clarified
- Validity means impossibility of true premises with a false conclusion; it concerns form, not truth.
- Soundness requires validity plus true premises, guaranteeing a true conclusion.
Contradictions Cause Logical Explosion
- From a contradiction, anything follows (ex falso quodlibet), so contradictions 'explode' a system.
- Paraconsistent logics avoid explosion, but classical systems ban contradictions to preserve useful inference.
