Though not yet an "official" project, Google has released a Bitcoin client. As you may remember, there were concerns here about what the government/legal reaction to Bitcoin [1] will be, and the significance of certain groups lending their support to it.  EFF and SIAI accept Bitcoin donations, which helps, and this action by Google is another big step.

Previous articles: SIAI accepting Bitcoin donations, Discussion on making money with Bitcoin (Clippy warning on the latter)

[1] In short, it's an anonymous P2P crypto-currency with no transaction fees, in which new units are generated by spending computer cycles computing hashes until you find one with specific properties.

Sorry for the self-centered post, but I don’t get many chances to be where there are a lot of rationalists.  (We’ve counted about four in all of Texas that go to this site.)

Thanks to the Cosmos’s noticing my need for a place to spend my vacation time this year, I will be staying in his NYC apartment while he’s gone.  I’ll definitely be at the NYC meetups.

So, if you are anywhere near this area and were interested in meeting me, let me know (either on this thread or privately) and we can work something out.

I’ve informed the NYC OB Google group, but figured there would be good opportunities to meet some of you that aren’t on that list or are a bit further away from the city.

In the interest of making decision theory problems more relevant, I thought I'd propose a real-life version of counterfactual mugging.  This is discussed in Drescher's Good and Real, and many places before.  I will call it the Hazing Problem by comparison to this practice (possibly NSFW – this is hazing, folks, not Disneyland).

The problem involves a timewise sequence of agents who each decide whether to "haze" (abuse) the next agent.  (They cannot impose any penalty on previous agent.)  For all agents n, here is their preference ranking:

1) not be hazed by n-1

2) be hazed by n-1, and haze n+1

3) be hazed by n-1, do NOT haze n+1

or, less formally:

1) not be hazed

2) haze and be hazed

3) be hazed, but stop the practice

The problem is: you have been hazed by n-1.  Should you haze n+1?

Like in counterfactual mugging, the average agent has lower utility by conditioning on having been hazed, no matter how big the utility difference between 2) and 3) is.  Also, it involves you having to make a choice from within a "losing" part of the "branching", which has implications for the other branches.

You might object the choice of whether to haze is not random, as Omega’s coinflip is in CM; however, there are deterministic phrasings of CM, and your own epistemic limits blur the distinction.

UDT sees optimality in returning not-haze unconditionally.  CDT reasons that its having been hazed is fixed, and so hazes.  I *think* EDT would choose to haze because it would prefer to learn that, having been hazed, they hazed n+1, but I'm not sure about that.

I also think that TDT chooses not-haze, although this is questionable since I'm claiming this is isomorphic to CM.  I would think TDT reasons that, "If n's regarded it as optimal to not haze despite having been hazed, then I would not be in a position of having been hazed, so I zero out the disutility of choosing not-haze."

Thoughts on the similarity and usefulness of the comparison?

Non-political follow-up to: Ungrateful Hitchhikers (offsite)

Related to: Prices or Bindings?, The True Prisoner's Dilemma

Summary: Situations like the Parfit's Hitchhiker problem select for a certain kind of mind: specifically, one that recognizes that an action can be optimal, in a self-interested sense, even if it can no longer cause any future benefit.  A mind that can identify such actions might put them in a different category which enables it to perform them, in defiance of the (futureward) consequentialist concerns that normally need to motivate it.  Our evolutionary history has put us through such "Parfitian filters", and the corresponding actions, viewed from the inside, feel like "something we should do", even if we don’t do it, and even if we recognize the lack of a future benefit.  Therein lies the origin of our moral intuitions, as well as the basis for creating the category "morality" in the first place.

Introduction: What kind of mind survives Parfit's Dilemma?

Parfit's Dilemma – my version – goes like this: You are lost in the desert and near death.  A superbeing known as Omega finds you and considers whether to take you back to civilization and stabilize you.  It is a perfect predictor of what you will do, and only plans to rescue you if it predicts that you will, upon recovering, give it $0.01 from your bank account.  If it doesn’t predict you’ll pay, you’re left in the desert to die. [1]

So what kind of mind wakes up from this?  One that would give Omega the money.  Most importantly, the mind is not convinced to withhold payment on the basis that the benefit was received only in the past.  Even if it recognizes that no future benefit will result from this decision -- and only future costs will result -- it decides to make the payment anyway.

Related to: Math is subjunctively objective, How to convince me that 2+2=3

Elaboration of points I made in these comments: first, second

TL;DR Summary: Mathematical truths can be cashed out as combined claims about 1) the common conception of the rules of how numbers work, and 2) whether the rules imply a particular truth.  This cashing-out keeps them purely about the physical world and eliminates the need to appeal to an immaterial realm, as some mathematicians feel a need to.

Background: "I am quite confident that the statement 2 + 3 = 5 is true; I am far less confident of what it means for a mathematical statement to be true." -- Eliezer Yudkowsky

This is the problem I will address here: how should a rationalist regard the status of mathematical truths?  In doing so, I will present a unifying approach that, I contend, elegantly solves the following related problems:

- Eliminating the need for a non-physical, non-observable "Platonic" math realm.

- The issue of whether "math was true/existed even when people weren't around".

- Cashing out the meaning of isolated claims like "2+2=4".

- The issue of whether mathematical truths and math itself should count as being discovered or invented.

- Whether mathematical reasoning alone can tell you things about the universe.

- Showing what it would take to convince a rationalist that "2+2=3".

- How the words in math statements can be wrong.