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RS143 - Scott Aaronson on "The theorem that proves rationalists can't disagree"

Release date: September 20, 2015

Scott AaronsonCan rational people disagree? This episode of Rationally Speaking features guest Scott Aaronson. Scott is a professor of computer science at MIT and has written about "Aumann's Agreement Theorem," which is related to Bayesian probability theory and seems to imply that two people cannot rationally disagree after they've shared their opinions and information with each other. Julia and Scott discuss how to reconcile Aumann's theorem with real-world disagreements, and explore the disconcerting question: Why should you favor your own beliefs, just because they're yours?


Scott's pick: Any book by Rebecca Goldstein, starting with "The Mind Body Problem."

 Full Transcripts 

Reader Comments (8)

Relating to the idea that most people throughout history believed in a god and I don't:

Scott summaries Aumann's theorem summary including the assumption that both agents are Bayesian. As you discussed, it seems fairly obvious that humans aren't inherently Bayesian agents. Some people are intuitively somewhat Bayesian, most of us took a lot of education and still don't follow Bayesian rules even if we logically understand them.

That, to me, suggests that this theorem is at best partially applicable in any real conversation and is not applicable if you believe that one party is largely non-Bayesian in his/her belief update system. Further, the reasonable baseline for normal interaction is that the other party is not Bayesian - nor that I am perfectly Bayesian, for that matter. Intuitively: If I don't have faith in your ability to generate rational beliefs, then it's not rational for me to give them any significant weight in my belief system.
September 22, 2015 | Unregistered CommenterDaniel
His remark that there might be something that we don't understand about quantum mechanics seems a wild understatement in light of 80 years of debate about multiple universes and whether the moon is there when nobody looks.
September 23, 2015 | Unregistered CommenterVector
Re Vector: Debates about how to understand quantum measurement, 'wavefunction collapse' etc (which are the debates you reference) do not have any bearing on whether quantum computing is possible. In other words, every minimal resolution of these questions says that quantum computing is possible. What Scott meant is that perhaps quantum mechanics is incorrect in some way that we are currently not aware of, but which would mean that quantum computing will not work. (Interestingly, most of the simple ways one can think of to break quantum mechanics would actually make quantum computing more powerful, not less!)
September 23, 2015 | Unregistered CommenterTyle
How much of the arguments against quantum computing do you know? I'd love to know more about the particular concerns. I have looked around briefly but not seen any specific arguments against the possibility of their construction. If you know of any articles where their feasibility is questioned or even which researches have maintained that it was highly suspect or critical of the approach I would appreciate if you (or anyone ) could point me in the right direction, Thanks ...Vector Shift.
September 23, 2015 | Unregistered CommenterVector
RE tyle...
I'm more than a little embarrassed. I tried to look you up to see if you had any ties to the subject but didn't get very far. Then I Googled "quantum computing can't work" and came up with "Lecture 14, Scepticism of Quantum Computing" , right to the point. Then I thought the name looked familiar. Yep. Scott Arronson the guest on the pod-cast ! I'm glad that at least I said that I had only looked around BRIEFLY ! Well, thanks for your comment and I have some reading to do.
Vector Shift.
September 24, 2015 | Unregistered CommenterVector
The fact that we don't see Aumann's result more in the real world I think is simply because most people aren't rational or don't act rationally most of the time.
October 14, 2015 | Unregistered CommenterChris J.
Great episode ! I love the podcast. : )

When I first heard about Aumann's agreement theorem, it surprised me that humans thought it was surprising. The idea that we shouldn't give more weight to an opinion merely because it was produced by our own brains should follow naturally from a view of opinion-making as truth-seeking, as opposed to a typical view of opinion-making as personal achievement-seeking. If we merely copy beliefs from those whom we recognise as our intellectual superiors, then those opinions don't really count as our own achievements, and that's one of the reasons we're reluctant to copy or update.

The counter-intuitiveness of the theorem could perhaps be caused by the fact that we've all grown up on the sub-optimal rationalist advice of "you should think for yourself". Sure, we should apply "fresh thinking" to answer questions, but that is often misinterpreted to say that we shouldn't consider testimonial evidence. It seems to me that the advice, "you should think for yourself," is often more motivated by the achievement-seeking view of opinion-making than an attempt at finding truth.

[Excuse the brag, but I also have a point.]
October 15, 2015 | Unregistered CommenterTimo Timo
Indeed, politicians could benefit from an increase in rationality.

If someone disbelieves in God, then they should update their probability for the existence of God on the basis of all the people who believe in God. But, by how much? And given all the different religions and gods, which god? Also, does the multitude of different gods lower the update potential for belief in any particular god?

RSPC should get a sponsorship from RSPC recommends lots of books, and links to frequently.
December 15, 2017 | Unregistered CommenterJameson

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