# Thread: Post Your Favorite Thought Experiment

1. ## Post Your Favorite Thought Experiment

The Library of Babel thought experiment --

You enter a library and take a book off the shelf. You notice that it’s filled with seemingly random strings of characters.

You take another book off the shelf. Same thing.

You examine a few more books and notice that all the books are quite similar.

Each book has exactly 500 pages. Each page has exactly 40 lines. And each line has exactly 50 character slots.

You examine a few more books and estimate that there are roughly 100 potential characters (including a blank spaces) that can go into each character slot.

Hmmm. Interesting.

Then you notice a sign that says “START HERE.” You go there, pick the first book off the shelf, and see that every page is blank.

You pick up the next book. It has a single letter ‘A’ in the first character slot, and all the other pages are blank.

You pick up the third book. It has a single letter ‘B’ in the first character slot. And, again, all the other pages are blank.

Then you look out across the library, and the shelves go on and on as far as the eye can see.

Your best guess is that each book in this library is a unique combination of characters, and that, collectively, the books in the library cover all the combinations that can be formed in books of this nature.

You do some quick math and calculate that there must be 100^(500*40*50) books -- or 100^1,000,000 (one-hundred to the millionth power) books.

A vast number indeed.

Then you begin to wonder what books might be out there.

There must be:

• A copy of “Hamlet," -- take THAT, infinite monkeys!
• A copy of “Hamlet” with one typo.
• A copy of "Hamlet" with a different typo.
• A copy of “Hamlet” with two typos.
• An accurate 500-page biography of your life (from your birth until your death).
• An extremely elegant proof of the Reimann Hypothesis
• A book containing a cure for cancer.

Wow! Just wow!

This is exciting.

Those books are out there somewhere. You just know it.

You have a cure for cancer almost at your fingertips!

Then the reality of the situation hits you, and you realize that the odds of finding any book you might want to find are very, very, . . . in fact vanishingly, . . . slim..

The numbers are just too big.

And there you sit with mixed emotions -- torn between absolute wonder at what books must sit in this library, and abject depression because you’ll never find them.

2. Here is the problem for me. This is like if google were just a list of every single website in order from A -Z with no way to search. But much much bigger since every character combination up to ?? is there. The Immediate problem is that SOMETHING created these books....see where I'm going with this?

How would you go about finding clues to the cure for cancer in that library? All you have to go on is START HERE on A. But that's as arbitrary as the experiment itself.

3. That library isn't just a thought experiment. It's real, and it's right in front of you. Right now. No, I'm not talking about the internet. I'm talking about your monitor.

If it's possible to display the cure for cancer on a monitor, then that potential exists, right now, without any other lab equipment it could just be there, in your face. Any image that could possibly be displayed on your monitor, exists in the state space of your monitor.

4. Maybe we could generate a database of text files like in that library and just search it for a cancer cure? Relevant XKCD.

5. Here is the problem for me. This is like if google were just a list of every single website in order from A -Z with no way to search. But much much bigger since every character combination up to ?? is there. The Immediate problem is that SOMETHING created these books....see where I'm going with this?
That you've forgotten the "thought" in thought experiment?

/extra credit: assuming i've given you a magical index for any book you wish in the library, calculate how long it would take for you to physically move to its location, and how fast you'd have to travel to get to it before you die :P

6. Not to mention, the library would need to be many orders of magnitude larger than the observable universe to house that many books.

The only thing that comes to mind for a thought experiment is Schroedinger's Cat, so I guess that makes it my favorite by default.

One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.

It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

7. Originally Posted by ACow
That you've forgotten the "thought" in thought experiment?

/extra credit: assuming i've given you a magical index for any book you wish in the library, calculate how long it would take for you to physically move to its location, and how fast you'd have to travel to get to it before you die :P

Problem is not solvable unless you specify the book density.

8. I really like the China brain thought experiment. If everyone in China performed the action of one neuron in a human brain, would the collective people of China have the same consciousness as one human (albeit really slower)?

I love this one not because of the materialistic vs dualistic debate but because I love the concept of a meta-consciouness. Maybe humans in a group already do exhibit a kind of collective consciousness, maybe there could even be a consciousness for the whole human race!

9. I will let you make any assumptions about book density, size, type and dimension of book storage :P I can be really easy and suggest a nice early book like "green eggs and ham" by doctor seuss. I'm sure that even with really outrageous assumptions, it will still be an amusing answer. Lets say each book is 20 cms x 10 cms x 0.1 mm in dimensions. I can come up with more figures if anyone wants to try :P

Two more interesting question, although far more hypothetical: what is the density of books with an ISBN relative to books under a certain length in the library:P If you randomly selected books from said library, would you ever pull find a useful coherent book before you died?

10. I really like the China brain thought experiment.
I've always liked the Chinese Room. From wikipedia:

Searle's thought experiment begins with this hypothetical premise: suppose that artificial intelligence research has succeeded in constructing a computer that behaves as if it understands Chinese. It takes Chinese characters as input and, by following the instructions of a computer program, produces other Chinese characters, which it presents as output. Suppose, says Searle, that this computer performs its task so convincingly that it comfortably passes the Turing test: it convinces a human Chinese speaker that the program is itself a live Chinese speaker. To all of the questions that the person asks, it makes appropriate responses, such that any Chinese speaker would be convinced that he or she is talking to another Chinese-speaking human being.
The question Searle wants to answer is this: does the machine literally "understand" Chinese? Or is it merely simulating the ability to understand Chinese?[7][b] Searle calls the first position "strong AI" and the latter "weak AI".[c]
Searle then supposes that he is in a closed room and has a book with an English version of the computer program, along with sufficient paper, pencils, erasers, and filing cabinets. Searle could receive Chinese characters through a slot in the door, process them according to the program's instructions, and produce Chinese characters as output. If the computer had passed the Turing test this way, it follows, says Searle, that he would do so as well, simply by running the program manually.
Searle asserts that there is no essential difference between the roles of the computer and himself in the experiment. Each simply follows a program, step-by-step, producing a behavior which is then interpreted as demonstrating intelligent conversation. However, Searle would not be able to understand the conversation. ("I don't speak a word of Chinese,"[10] he points out.) Therefore, he argues, it follows that the computer would not be able to understand the conversation either.
Searle argues that without "understanding" (or "intentionality"), we cannot describe what the machine is doing as "thinking" and since it does not think, it does not have a "mind" in anything like the normal sense of the word. Therefore he concludes that "strong AI" is false.
The philosophical zombie is cool too:

A philosophical zombie or p-zombie in the philosophy of mind and perception is a hypothetical being that is indistinguishable from a normal human being except in that it lacks conscious experience, qualia, or sentience.[1] For example, a philosophical zombie could be poked with a sharp object, and not feel any pain sensation, but yet, behave exactly as if it does feel pain (it may say "ouch" and recoil from the stimulus, or tell us that it is in intense pain).
The notion of a philosophical zombie is used mainly in thought experiments intended to support arguments (often called "zombie arguments") against forms of physicalism such as materialism, behaviorism and functionalism. Physicalism is the idea that all aspects of human nature can be explained by physical means: specifically, all aspects of human nature and perception can be explained from a neurobiological standpoint. Some philosophers, like David Chalmers, argue that since a zombie is defined as physiologically indistinguishable from human beings, even its logical possibility would be a sound refutation of physicalism.[2] However, physicalists like Daniel Dennett counter that Chalmers's physiological zombies are logically incoherent and thus impossible.

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