Graham Priest on Dialetheism, True Contradictions, the Liar Paradox & Why Classical Logic Isn’t Enough

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What if some contradictions are not mistakes — but truths?

For over 2,500 years, Western philosophy has treated contradiction as catastrophic. From Aristotle’s law of non-contradiction to modern formal systems, logic has operated under one sacred assumption: a statement cannot be both true and false.

But what if that assumption is wrong?

In this deep, wide-ranging conversation, I sit down with Graham Priest, one of the world’s most influential philosophers of logic and the leading defender of dialetheism — the view that some contradictions are true.

We explore:

• What dialetheism really means
• Why the liar paradox still unsettles logicians
• How paraconsistent logic blocks “explosion” (the idea that from a contradiction, anything follows)
• Whether classical logic is incomplete rather than universal
• What Buddhist philosophy and Nāgārjuna understood about contradiction
• And whether AI systems may eventually require non-classical logics to model human reasoning

Far from being an abstract puzzle, the liar paradox exposes deep tensions in how we understand truth, self-reference, and rationality itself. If contradictions can be true, then the foundations of logic, mathematics, metaphysics — and even artificial intelligence — may need rethinking.

We also move beyond formal systems into lived philosophy:

• Graham’s journey from Christianity to atheism
• His engagement with Buddhist thought
• The limits of decision theory
• The discipline of karate as a philosophical practice

This is not merely a discussion of symbolic logic.

It is a conversation about the limits of reason.

About what happens when our most trusted intellectual tools reach their breaking point.

And about whether embracing contradiction might expand — rather than destroy — rational inquiry.

If your background is in technology, computer science, AI, or engineering, this episode may challenge assumptions you didn’t even realize you were making.

If your background is in philosophy, it may unsettle what you thought was settled.

And if you care about the future of thought itself, this conversation is essential.

As always, you can listen to or download the audio file above or scroll down and watch the video interview in full. To show your support, you can write a review on iTunes, make a direct donation, or become a patron on Patreon.

Who is Graham Priest?

Graham Priest grew up in South London and studied mathematics at St. John’s College, Cambridge, before earning his doctorate in mathematics from the London School of Economics. During this time, he discovered that philosophy fascinated him even more than mathematics, and in 1974, he began his academic career in a philosophy department at the University of St Andrews. His move marked the beginning of a lifelong engagement with logic, metaphysics, and the foundations of thought.

Priest spent much of his career in Australia, holding positions at the University of Western Australia, the University of Queensland, and later the Boyce Gibson Chair of Philosophy at the University of Melbourne, where he is now emeritus. He has also served as President of both the Australasian Association for Logic and the Australasian Association of Philosophy, was elected a Fellow of the Australian Academy of Humanities, and in 2009 became Distinguished Professor at the Graduate Center of the City University of New York, where he currently lives and works.

Widely regarded as one of the world’s leading philosophers of logic, Priest has published roughly 240 papers and several major books, most notably on non-classical logic and dialetheism — the view that some contradictions are true. His work spans metaphysics, Buddhist philosophy, and the history of philosophy, both East and West. Beyond academia, he has lectured internationally, practiced karate to a high rank, and maintains a lifelong appreciation for music and East Asian art, bringing together intellectual rigor, cultural breadth, and lived philosophical practice.