Category
Logic & argument
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Reading group: Prior Analytics I.1–7, slowly, with a Nyāya inference on the table
Everyone says Aristotle invented formal logic, and I realise I have never read the Prior Analytics closely in company. So here is a proposal: the first seven chapters of Book I, over five weeks, which is where the whole assertoric system is…
Started by Giulia Ferrante6 replies -
Nāgasena’s condition for talking with a king: argue as scholars do, not as kings do
Early in the Milindapañha, the Questions of King Milinda, the king asks the monk Nāgasena to discuss with him. Nāgasena answers with a condition. He will talk if the king will talk as scholars do, not as kings do. What's the difference?…
Started by Nirmala Jayasekara5 replies -
Frege and Husserl started on the same side. What was the psychologism dispute about?
I've been reading about the split between analytic and continental philosophy because my colleagues treat it as two tribes. What surprised me is that both traditions are said to trace back, around 1900, to two men who agreed about something: Frege and…
Started by Pieter van Dijkhuizen5 replies -
Navya-Nyāya’s language of limitors, and what it was built to do
Every few months someone tells me that Navya-Nyāya was "Indian predicate logic". I'd like to test that claim with people who know Frege better than I do. The school is usually dated from Gaṅgeśa's Tattvacintāmaṇi in the fourteenth century. What Gaṅgeśa and…
Started by Meera Kulkarni5 replies -
Logic is the one part of philosophy that settles questions, and the rest should take note
People like to say that philosophy never makes progress, that we're still arguing about the same questions as Plato. Logic is the counterexample. For two thousand years, Aristotle's syllogistic could not handle inferences involving relations. "Every horse is an animal, so every…
Started by Derek Hollis5 replies -
Outside a courtroom, who should carry the burden of proof?
In court the burden of proof is fixed by rules. In a criminal case the prosecution must prove guilt beyond reasonable doubt; in a civil case the claimant must win on the balance of probabilities. Islamic law has a well-known maxim to…
Started by Hamza Qureshi6 replies -
Predicate logic was discovered, not invented
Is logic discovered or invented? I want to argue that predicate logic is the strongest evidence that it is discovered. Consider the inference: every horse is an animal, so every horse's head is an animal's head. People knew for two thousand years…
Started by Tomasz Szewczak5 replies -
For ordinary speech, Aristotle was right: “All S are P” presupposes there are some S
Modern logic reads "All S are P" as "for anything, if it is S, it is P". If nothing is S, the statement comes out true automatically. So "All the unicorns in my garden are pink" is true, and so is "All…
Started by Oskar Nyberg6 replies -
Soundness and completeness of a logical system: what exactly is being proved?
I'm stuck on vocabulary, having no formal training in logic. I've read that a logical system can be sound and complete: everything provable is true, and everything true is provable. Fine. But then I read that Gödel proved a completeness theorem in…
Started by Pieter van Dijkhuizen4 replies -
If syllogistic logic couldn’t handle relations, why did it last two thousand years?
Working inside predicate logic every day, I'm often reminded how much it can do that the syllogism can't. The textbook example (usually credited to De Morgan) is: all horses are animals, therefore every head of a horse is the head of an…
Started by Derek Hollis6 replies -
Qiyās, kal va-chomer and legal analogy: defeasible reasoning with centuries of rules
The reasoning I heard most often from the bench, in all my years in court, was neither deduction nor statistics. It was analogy: this case resembles that one in the respect that matters, so it should be decided the same way. Islamic…
Started by Khalid Mahmood Awan5 replies -
Logic for beginners: what makes an argument valid
A first introduction to the single most useful idea in logic, with the tests you can use on any argument and the mistakes almost everyone makes.
Started by The EditorsReply first (no replies yet) -
Reading group: Stoic logic in Diogenes Laertius, Lives Book VII
Chrysippus is said to have written hundreds of books, a large share of them on logic, and almost all are lost. What we have of Stoic logic comes mostly through later writers: Diogenes Laertius, who gives a summary of Stoic dialectic in…
Started by Giulia Ferrante5 replies