Rationally Speaking #72 - Graham Priest on Paradoxes and Paraconsistent Logic

Rationally Speaking Podcast

New York City Skeptics

Society & Culture, Skepticism, Science, Philosophy

4.6 • 787 Ratings

🗓️ 21 October 2012

⏱️ 47 minutes

🔗️ Recording | iTunes | RSS

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Summary

Can a statement be simultaneously true and false? That might seem like sheer nonsense to you -- but not to certain modern logicians. In this episode Massimo and Julia are joined again by philosopher and logician Graham Priest, who explains why we have to radically revise our notions of "true" and "false." In the process, he explains classic puzzlers like the "barber paradox": "In a village, the barber shaves all men who do not shave themselves. Does he shave himself?" Follow along for an episode that really takes to heart the podcast's tagline: exploring the borderlands between reason and nonsense.

Transcript

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0:00.0	Rationally speaking is a presentation of New York City skeptics dedicated to promoting critical thinking, skeptical inquiry, and science education.
0:22.6	For more information, please visit us at NYCCEPTICs.org.
0:35.3	Welcome to rationally speaking, the podcast where we explore the borderlands between reason and nonsense. I am your host, Massimo Piliucci, and with me as always is my co-host, Julia Gileff.
0:44.8	Julia, what are we going to talk about today?
0:47.1	Massimo, this is the second of two episodes that we're taping with Graham Priest, who is the Boyce Gibson Professor of Philosophy at the University of
0:54.9	Melbourne and a distinguished professor of philosophy at CUNY Graduate Center in New York.
1:01.1	Our last episode with Graham, you may remember, was about Eastern philosophy. And this time,
1:06.5	we're going to talk to him about another specialty of his, which is paraconsistent logic.
1:11.5	So Graham will delve into this in a minute.
1:15.0	But just to offer a teaser, it may seem like incredibly self-evident, like one of the most self-evident truths there could possibly be that something can't be simultaneously true and false. Well, that
1:29.3	is a self-evident truth we are going to call into question today. So, Graham, could you give
1:34.3	our listeners just a brief definition of what paraconsistent logic is? Okay. If you go to a university
1:43.1	and you take a first course in logic, you will almost certainly be taught that once you have a contradiction, everything follows from that.
1:54.0	A contradiction being...
1:56.0	Well, let me give you an example.
1:58.0	You will be taught that if you suppose that the sun is and is not made of green cheese,
2:06.3	it follows that I'm a frog.
2:09.8	Clearly.
2:10.6	Obviously, right.
2:11.4	Okay.
2:11.7	And why is that?
2:14.4	Okay, let's not go into two technical details for the moment.
	...

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