Saturday, January 10, 2015

The Parable of the Free Beer

There is a classic logic problem that goes like this: you are on an island where some of the natives always lie and others always tell the truth.  You find yourself at a fork in the road where one branch leads to the village, the other into the jungle, and you wish to determine which branch is which.  There is a native standing at the fork, of whom you may ask one yes-no question.  What do you ask?

The usual, nerdy answer goes something like, "If I were to ask you if the left path is the way to the village, would you say yes?"  The problem with this answer is that the native may as well decide that by the time he sorts out the hypotheticals, the cannibals will have emerged from the jungle and had both of you for lunch.  So in the real world (and I may as well warn you now, this post will require a certain level of suspension of disbelief) he is as likely to say, "Bugger off" or "WTF?" as he is to say yes or no.

Martin Gardner suggested a brilliant, practical solution: you should ask, "Did you know they are serving free beer in the village?"  Then you ignore the answer, and just follow the villager whichever way he goes.

This solution is cute, but not without its issues.  It assumes, for example, that your interlocutor likes beer, that he doesn't have urgent business in the jungle, that he is not an "artful deceiver" willing to forego a shot at free beer in order to mislead a foreigner, etc.  Furthermore, it assumes that the native is not considering the possibility that you might be a deceiver, and that you are asking the question not because there is, in point of fact, free beer in the village, but that you have (as indeed you do) some hidden agenda that has nothing at all to do with beer.

In this post I want to consider the inverse problem: suppose you know the way to the village and a native comes up to you and says, "Did you know they are serving free beer in the village?"  How would you respond?  Assume for the sake of argument that you like beer, and all else being equal you'd rather pay less than more.  But in this case all else is not equal.  To act on the information that is (apparently) being provided to you, you have to walk to the village.  If you get there and discover that they are not, in fact, serving free beer then you have incurred, at the very least, an opportunity cost.  Since you are wise in the ways of wily natives, you decide to make further inquiries, and the following conversation ensues:

You: No, I did not know they are serving free beer in the village.  Are they in fact serving free beer in the village, or are you trying to trick me into showing you the way to the village?  Because if it's the latter, all you have to do is ask.  This isn't a logic puzzle.

Native: Oh no, I assure you, there is no trickery, and I have no hidden agenda.  They are indeed serving free beer in the village.  Do you like beer?

You: Indeed I do.

Native: Then why are you not at this very moment rushing off to the village?  It's right over there.

You: It's because I'm a little skeptical.  It seems odd that they should be serving free beer.  As far as I know, there is no reason for them to be doing so.  Is there a festival going on that I didn't hear about?  Or maybe the beer company is running a promotion?

Native: No, nothing like that.  The barkeep is just a particularly generous fellow.

You: I see.  So he sometimes serves free beer just out of the goodness of his heart, does he?

Native: Not sometimes.  Always.  Twenty-four by seven.  All you have to do is walk into the pub and ask.

You: That seems a tad implausible.  How does he stay in business?

Native: Tips.

You: You'll have to pardon me if I'm not convinced.

Native: Oh, it's true.  Ask anyone.  Say, Fred, come over here a second?

Fred: What can I do for you?

Native: This foreigner here doesn't believe that they serve free beer in the village.

Fred: Oh, they do.  I've availed myself of it many times.

[So you go to the village and enter the bar.]

Barkeep: Welcome, stranger!  What can I get for you?

You: I hear you're serving free beer.

Barkeep: Indeed we are.  And not just any old beer.  It's the best beer you've ever had.

You: Can't wait to try it.

Barkeep: Well, as soon as you're dead, you can.

You: What?!

Barkeep:  Oh yeah, didn't they tell you?  You can only have this beer in the afterlife.

You: I knew there had to be a catch.

Barkeep: It's not a catch.  This beer is so good that if you had it while you were alive your head would explode.

You: Do you have any idea how ridiculous that sounds?

Barkeep: Yeah, I know, but it's true.

You: What makes you think so?

Barkeep: Oh, the evidence is overwhelming.  People have written books about the beer.  2000 years ago people were actually able to try it.  And even today, while you can't actually drink it until after you're dead, you can experience it.

You: How?  (And what does it even mean to experience beer without drinking it?)

Barkeep: You have to believe in the beer, and then the beer will reveal itself to you.

You: That is the most absurd thing I have ever heard in my life.

Barkeep: Be that as it may, you really want to believe in the beer.

You: Why?

Barkeep: Because if you don't then when you die you will go to the Hostelry of Eternal Liquor Lossage, which is a very bad place.

You: What makes it such a bad place?

Barkeep: No beer.

You: Hm, that does sound unpleasant.  Can I take some time to think about it?

Barkeep: Sure, but don't take too long.  Once you're dead, that's it, no do-overs.  And you never know when you might get hit by a bus.

You: I'll be careful.  Thank you, and good bye.

Barkeep:  Good bye. Oh, before you go, take a copy of the Beer Insider's and Brew Lover's Encyclopedia.  It will tell you all about the beer.  How it was made, what makes it so special, why you can't get it any more except after you're dead...

[He hands you a thick book.]

You: Thank you.

[You exit the bar, making a mental note to be very careful to look both ways before you cross the street.  On the sidewalk outside you encounter another villager.]

Villager: Say, stranger, did you know that they are serving free wine in the next village?


Publius said...

You should really tell people your other jungle story - when you got lost in the jungle. You had gotten separated from your exploration team in mid-morning. By afternoon, you were quite tired, hot, dehydrated, and quite a bit hungry. It was at this point you come upon a river. Moving along the bank didn't seem like a good idea, as one direction led to a swampy area and the other direction to a substantial growth of thorny plants. So you decided to cross the river.

You entered the water and started swimming across. Mid-way across, though, you grew tired of fighting the current and started sinking. Not knowing what to do, you thrashed in place, trying to catch a breath of fresh air, and screaming for help. You were lost in a middle of a jungle, though, so you knew there was no one to help. You started to lose hope, then your strength, and you sank under the water again thinking the end is at hand.

Suddenly, though, you feel a strong hand grab your left arm and pull you up to the surface. As you gasp and choke, you see the man who has pulled you up from the depths, pulled you up from death. He holds you close and begins swimming you to the opposite bank. As he swims to get you to safety, you realize you have been saved. You reach the bank and the man carries you up the bank.

Tragically, though, the man falls backwards into the river. He floats to the center of the river. He loses strength, and he struggles to keep his head above water. He is in pain, and his struggles only end when he sinks underneath the water. You see him die from the river bank. Turning away from the river, you see that he had set you down in sight of a footpath. A sign of people! You follow the footpath and it leads to the village.

Entering the village, you go the bar. The bar was packed with patrons - apparently it was "Free Beer Friday." You enter, get a beer, and tell all the patrons your incredible story. How you were lost in the jungle, started to drown swimming across a river, yet were suddenly lifted up by a caring man, who swam you to the opposite bank and sat you down. Then, he fell back into the river and died. All the patrons listened in rapt attention as you told your story.

And none of them believed you.

Ron said...

Why wouldn't they believe you? That is a perfectly plausible story.

But that story is *not* an analog of the Christian story. You left out some important bits. The Christian story starts the way you describe, but it then goes on to say: oh, by they way, you think you're sitting at a bar having a beer, but you're really not. You're actually drowning in this river too, even though you may not realize it. And the *reason* that you're drowning in the river is no fault of your own, it has to do with something that one of your ancestors did six thousand years ago or so. And the *only* way to get out is to ask this mystery man for help. No matter how hard you try, you can't swim out yourself, nor can any of your fellow mortals save you (because you are *all* drowning simultaneously!) But the mystery man can help you because he didn't really drown in the river, he came back to life. But you didn't actually see him drown and come back, you just read about it in a book. And you didn't actually see him in the river, you just felt his presence. And if you don't ask the mystery man for help, your suffering will not end when you die. Instead, you will burn in eternal hell fire. (Oh, and the mystery man is the one who set this all up. And he loves you.)

*That* is the Christian story, or at least it's *a* Christian story. There are many variations on the theme. But that's the mainstream (no pun intended) Protestant version. Do you see how it becomes a little less plausible once you add these details?

Publius said...

Pardonnez-moi, mais je ne ai que 4096 caractères.

Here's another take on it.

>You're actually drowning in this river too, even though you may not realize it.

I would think most people realize it?

>And the *reason* that you're drowning in the river is no fault of your own,

"Fault" or "guilt" does not pass to you from the concept of original sin.

>it has to do with something that one of your ancestors did six thousand years ago or so.

That's not right. The Earth is 4.5 billion years old. The first life was microbial mats, which were the only life for about 2 billion years. Notable animals after that are the dinosaurs, which lived between 201 and 66 million years ago (Ma) - the dominant terrestrial vertebrate for 135 million years.[1] Ancient ancestors of humans appeared 2.3 Ma, and the modern human form emerged only 200,000 years ago. Modern human behavior only began 50,000 years ago. When the sun finally turns into a red giant, it could turn out that the dinosaurs had the longest persistence on Earth.

[1] The first stegosaurs evolved 176 Ma.

Ron said...

> I would think most people realize it?

I think it comes as unpleasant news to most people that they are Totally Depraved.

> "Fault" or "guilt" does not pass to you from the concept of original sin.

All I know is what I'm told: I'm going to burn in hell for all eternity unless I am saved by God's grace. I don't really care what label you attach to it. What I care about is whether there is any reason to believe that it is actually true. Is there one? If so, what is it?

> >it has to do with something that one of your ancestors did six thousand years ago or so.
> That's not right.

The street evangelists say it is right. So does Irenaeus. Why should I believe you and not them?

> The Earth is 4.5 billion years old.

Ken Ham says it's 6000 years old. Why should I believe you and not him?

BTW, it would help if you would tell me what your theology actually is.