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- Frequently Asked Questions (FAQS);faqs.457
-
-
-
- My impression from the black and white plates of the Voynich MS I've seen, are
- that the illustrations are very weird when compared to other 'illuminated'
- manuscripts of this time. Particularly I would say that there is emphasis
- on the female nude that is unusual for the art of this period. I can't say
- that I myself believe the images to have ANYTHING to do with the text.
- My own conjecture is that the manuscript is a one-way encipherment. A
- cipher so clever that the inventor didn't even think of how it could be
- deciphered. Sorta like an /etc/passwd file.
-
- Bibliography
- ------------
- 1. William R. Newbold. _The Cipher of Roger Bacon_Roland G Kent, ed.
- University of Pennsylvania Press, 1928.
- 2. Joseph Martin Feely. _Roger Bacon's Cipher: The Right Key Found_
- Rochester N.Y.:Joseph Martin Feely, pub., 1943.
- 3. _The Most Mysterious Manuscript_ Robert S. Brumbaugh, ed. Southern Illinois
- Press, 1978
-
-
- Unix filters are so wonderful. Massaging the machine readable file, we find:
-
- 4182 "words", of which 1284 are used more than once, 308 used 8+ times,
- 184 used 15+ times, 23 used 100+ times.
-
- Does this tell us anything about the language (if any) the text is written
- in?
-
- For those who may be interested, here are the 23 words used 100+ times:
- 121 2
- 115 4OFAE
- 114 4OFAM
- 155 4OFAN
- 195 4OFC89
- 162 4OFCC89
- 101 4OFCC9
- 189 89
- 111 8AE
- 492 8AM
- 134 8AN
- 156 8AR
- 248 OE
- 148 OR
- 111 S9
- 251 SC89
- 142 SC9
- 238 SOE
- 150 SOR
- 244 ZC89
- 116 ZC9
- 116 ZOE
-
-
-
- Could someone email the Voynich Ms. ref list that appeared here not
- very long ago? Thanks in advance...
-
- Also... I came across the following ref that is fun(?):
-
- The Voynich manuscript: an elegant enigma / M. E. D'Imperio
- Fort George E. Mead, Md. : National Security Agency(!)
- Central Security Service(?), 1978. ix, 140 p. : ill. ; 27 cm.
-
- The (?!) are mine... Sorry if this was already on the list, but the
- mention of the NSA (and what's the CSS?) made it jump out at me...
-
- --
- Ron Carter | rcarter@nyx.cs.du.edu rcarter GEnie 70707.3047 CIS
- Director | Center for the Study of Creative Intelligence
- Denver, CO | Knowledge is power. Knowledge to the people. Just say know.
-
-
-
- Distribution: na
- Organization: Wetware Diversions, San Francisco
- Keywords:
-
-
- From sci.archaeology:
- >From: jamie@cs.sfu.ca (Jamie Andrews)
- >Date: 16 Nov 91 00:49:08 GMT
- >
- > It seems like the person who would be most likely to solve
- >this Voynich manuscript cipher would have
- >(a) knowledge of the modern techniques for solving more complex
- > ciphers such as Playfairs and Vigineres; and
- >(b) knowledge of the possible contemporary and archaic languages
- > in which the plaintext could have been written.
-
- An extended discussion of the Voynich Manuscript may be found in the
- tape of the same name by Terence McKenna. I'm not sure who is currently
- publishing this particular McKenna tape but probably one of:
- Dolphin Tapes, POB 71, Big Sur, CA 93920
- Sounds True, 1825 Pearl St., Boulder, CO 80302
- Sound Photosynthesis, POB 2111, Mill Valley, CA 94942
-
- The Spring 1988 issue of Gnosis magazine contained an article by McKenna
- giving some background of the Voynich Manuscipt and attempts to decipher
- it, and reviewing Leo Levitov's "Solution of the Voynich Manuscript"
- (published in 1987 by Aegean Park Press, POB 2837 Laguna Hills, CA 92654).
- Levitov's thesis is that the manuscript is the only surviving primary
- document of the Cathar faith (exterminated on the orders of the Pope in
- the Albigensian Crusade in the 1230s) and that it is in fact not
- encrypted material but rather is a highly polyglot form of Medieval
- Flemish with a large number of Old French and Old High German loan
- words, written in a special script.
-
- As far as I know Levitov's there has been no challenge to Levitov's
- claims so far.
-
-
-
- Michael Barlow, who had reviewed Levitov's book in Cryptologia, had sent me
- photocopies of the pages where much of the language was described
- (pp.21-31). I have just found them, and am looking at them now as I am
- typing this. Incidentally, I do not believe this has anything to do with
- cryptology proper, but the decipherment of texts in unknown languages. So
- if you are into cryptography proper, skip this.
-
- Looking at the "Voynich alphabet" pp.25-27, I made a list of the letters of
- the Voynich language as Levitov interprets them, and I added phonetic
- descriptions of the sounds I *think* Levitov meant to describe. Here it is:
-
- Letter# Phonetic Phonetic descriptions
- (IPA) in linguists' jargon: in plain English:
-
- 1 a low open, central unrounded a as in father
- e mid close, front, unrounded ay as in May
- O mid open, back, rounded aw as in law
- or o as in got
- (British
- pronunciation)
-
- 2 s unvoiced dental fricative s as in so
- 3 d voiced dental stop d
- 4 E mid, front, unrounded e as in wet
- 5 f unvoiced labiodental fricative f
- 6 i short, high open, front, i as in dim
- unrounded
- 7 i: long, high, front, unrounded ea as in weak
-
- 8 i:E (?) I can't make head nor tail of Levitov's
- explanations. Probably like "ei" in "weird"
- dragging along the "e": "weeeird"! (British
- pronunciation, with a silent "r")
- 9 C unvoiced palatal fricative ch in German ich
- 10 k unvoived velar stop k
-
- 11 l lateral, can't be more precise from
- description, probably like l in "loony"
-
- 12 m voiced bilabial nasal m
- 13 n voiced dental nasal n
- 14 r (?) cannot tell precisely from Scottish r?
- description Dutch r?
- 15 t no description; dental stop? t
- 16 t another form for #15 t
- 17 T (?) no description th as in this?
- th as in thick?
- 18 TE (?) again, no description
- or ET (?)
- 19 v voiced labiodental fricative v as in rave
- 20 v ditto, same as #19 ditto
-
- (By now, you will have guessed what my conclusion about Levitov's
- decipherment was)
-
- In the column headed "Phonetic (IPA)" I have used capital letters for lack
- of the special international phonetic symbols:
-
- E for the Greek letter "epsilon"
- O for the letter that looks like a mirror-image of "c"
- C for c-cedilla
- T for the Greek letter "theta"
-
- The colon (:) means that the sound represented by the preceding letter is
- long, e.g. "i:" is a long "i".
-
- The rest, #21 to 25, are not "letters" proper, but represent groups
- of two or more letters, just like #18 does. They are:
-
- 21 av
- 22a Ev
- 22b vE
- 23 CET
- 24 kET
- 25 sET
-
- That gives us a language with 6 vowels: a (#1), e (#1 again), O (#1 again),
- E (#4), i (#6), and i: (#7). Letter #8 is not a vowel, but a combination
- of two vowels: i: (#7) and probably E (#4). Levitov writes that the
- language is derived from Dutch. If so, it has lost the "oo" sound (English
- spelling; "oe" in Dutch spelling), and the three front rounded vowels of
- Dutch: u as in U ("you", polite), eu as in deur ("door"), u as in vlug
- ("quick"). Note that out of six vowels, three are confused under the same
- letter (#1), even though they sound very different from one another: a, e,
- O. Just imagine that you had no way of distinguishing between "last",
- "lest" and "lost" when writing in English, and you'll have a fair idea of
- the consequences.
-
- Let us look at the consonants now. I will put them in a matrix, with the
- points of articulation in one dimension, and the manner of articulation in
- the other (it's all standard procedure when analyzing a language). Brackets
- around a letter will mean that I could not tell where to place it exactly,
- and just took a guess.
-
- labial dental palatal velar
- nasal m n
- voiced stop d
- unvoiced stop t k
- voiced fricative v (T)
- unvoiced fricative f s C
- lateral l
- trill (?) (r)
-
- Note that there are only twelve consonant sounds. That is unheard of for a
- European language. No European language has so few consonant sounds.
- Spanish, which has very few sounds (only five vowels), has seventeen
- distinct consonants sounds, plus two semi-consonants. Dutch has from 18 to
- 20 consonants (depending on speakers, and how you analyze the sounds.
- Warning: I just counted them on the back of an envelope; I might have
- missed one or two). What is also extraordinary in Levitov's language is
- that it lacks a "g", and *BOTH* "b" and "p". I cannot think of one single
- language in the world that lacks both "b" and "p". Levitov also says that
- "m" occurs only word-finally, never at the beginning, nor in the middle of
- a word. That's true: the letter he says is an "m" is always word-final in
- the reproductions I have seen of the Voynich MS. But no language I know of
- behaves like that. All have an "m" (except one American Indian language,
- which is very famous for that, and the name of which escapes me right now),
- but, if there is a position where "m" never appears in some languages, that
- position is word-finally. Exactly the reverse of Levitov's language.
-
- What does Levitov say about the origin of the language?
-
- "The language was very much standardized. It was an application of a
- polyglot oral tongue into a literary language which would be understandable
- to people who did not understand Latin and to whom this language could be
- read."
-
- At first reading, I would dismiss it all as nonsense: "polyglot oral
- tongue" means nothing in linguistics terms. But Levitov is a medical
- doctor, so allowances must be made. The best meaning I can read into
- "polyglot oral tongue" is "a language that had never been written before
- and which had taken words from many different languages". That is perfectly
- reasonable: English for one, has done that. Half its vocabulary is Norman
- French, and some of the commonest words have non-Anglo-Saxon origins.
- "Sky", for instance, is a Danish word. So far, so good.
-
- Levitov continues: "The Voynich is actually a simple language because it
- follows set rules and has a very limited vocabulary.... There is a
- deliberate duality and plurality of words in the Voynich and much use of
- apostrophism".
-
- By "duality and plurality of words" Levitov means that the words are highly
- ambiguous, most words having two or more different meanings. I can only
- guess at what he means by apostrophism: running words together, leaving
- bits out, as we do in English: can not --> cannot --> can't, is not -->
- ain't.
-
- Time for a tutorial in the Voynich language as I could piece it together
- from Levitov's description. Because, according to Levitov, letter #1
- represent 3 vowels sounds, I will represent it by just "a", but remember:
- it can be pronounced a, e, or o. But I will distinguish, as does Levitov,
- between the two letters which he says were both pronounced "v", using "v"
- for letter #20 and "w" for letter #21.
-
- Some vocabulary now. Some verbs first, which Levitov gives in the
- infinitive. In the Voynich language the infinitive of verbs ends in -en,
- just like in Dutch and in German. I have removed that grammatical ending in
- the list which follows, and given probable etymologies in parentheses
- (Levitov gives doesn't give any):
-
- ad = to aid, help ("aid")
- ak = to ache, pain ("ache")
- al = to ail ("ail")
- and = to undergo the "Endura" rite ("End[ura]", probably)
- d = to die ("d[ie]")
- fad = to be for help (from f= for and ad=aid)
- fal = to fail ("fail")
- fil = to be for illness (from: f=for and il=ill)
- il = to be ill ("ill")
- k = to understand ("ken", Dutch and German "kennen" meaning "to know")
- l = to lie deathly ill, in extremis ("lie", "lay")
- s = to see ("see", Dutch "zien")
- t = to do, treat (German "tun" = to do)
- v = to will ("will" or Latin "volo" perhaps)
- vid = to be with death (from vi=with and d=die)
- vil = to want, wish, desire (German "willen")
- vis = to know ("wit", German "wissen", Dutch "weten")
- vit = to know (ditto)
- viT = to use (no idea, Latin "uti" perhaps?)
- vi = to be the way (Latin "via")
- eC = to be each ("each")
- ai:a = to eye, look at ("eye", "oog" in Dutch)
- en = to do (no idea)
- Example given by Levitov: enden "to do to death" made up of "en"
- (to do), "d" (to die) and "en" (infinitive ending). Well, to me,
- that's doing it the hard way. What's wrong with just "enden" = to
- end (German "enden", too!)
-
- More vocabulary:
-
- em = he or they (masculine) ("him")
- er = her or they (feminine) ("her")
- eT = it or they ("it" or perhaps "they" or Dutch "het")
- an = one ("one", Dutch "een")
-
- "There are no declensions of nouns or conjugation of verbs. Only the
- present tense is used" says Levitov.
-
- Examples:
-
- den = to die (infinitive) (d = die, -en = infinitive)
- deT = it/they die (d = die, eT = it/they)
- diteT = it does die (d = die, t = do, eT = it/they, with an "i" added to
- make it easier to pronounce, which is quite common and natural
- in languages)
-
- But Levitov contradicts himself immediately, giving another tense (known
- as present progressive in English grammar):
-
- dieT = it is dying
-
- But I may be unfair there, perhaps it is a compound: d = die, i = is
- ...-ing, eT = it/they.
-
- Plurals are formed by suffixing "s" in one part of the MS, "eT" in another:
- "ans" or "aneT" = ones.
-
- More:
-
- wians = we ones (wi = we, wie in Dutch, an = one, s = plural)
- vian = one way (vi = way, an = one)
- wia = one who (wi = who, a = one)
- va = one will (v = will, a = one)
- wa = who
- wi = who
- wieT = who, it (wi = who, eT = it)
- witeT = who does it (wi = who, t = do, eT = it/they)
- weT = who it is (wi = who, eT = it, then loss of "i", giving "weT")
- ker = she understands (k = understand, er =she)
-
- At this stage I would like to comment that we are here in the presence of a
- Germanic language which behaves very, very strangely in the way of the
- meanings of its compound words. For instance, "viden" (to be with death) is
- made up of the words for "with", "die" and the infinitive suffix. I am sure
- that Levitov here was thinking of a construction like German "mitkommen"
- which means "to come along" (to "withcome"). I suppose I could say "Bitte,
- sterben Sie mit" on the same model as "Bitte, kommen Sie mit" ("Come with
- me/us, please), thereby making up a verb "mitsterben", but that would mean
- "to die together with someone else", not "to be with death".
-
- Let us see how Levitov translates a whole sentence. Since he does not
- explain how he breaks up those compound words I have tried to do it using
- the vocabulary and grammar he provides in those pages. My tentative
- explanations are in parenthesis.
-
- TanvieT faditeT wan aTviteT anTviteT atwiteT aneT
-
- TanvieT = the one way (T = the (?), an = one, vi =way, eT = it)
- faditeT = doing for help (f = for, ad = aid, i = -ing, t = do, eT = it)
- wan = person (wi/wa = who, an = one)
- aTviteT = one that one knows (a = one, T = that, vit = know, eT = it.
- Here, Levitov adds one extra letter which is not in the text,
- getting "aTaviteT", which provide the second "one" of his
- translation)
- anTviteT = one that knows (an =one, T = that, vit = know, eT = it)
- atwiteT = one treats one who does it (a = one, t = do, wi = who,
- t = do, eT = it. Literally: "one does [one] who does it".
- The first "do" is translated as "treat", the second "one" is
- added in by Levitov: he added one letter, which gives him
- "atawiteT")
- aneT = ones (an = one, -eT = the plural ending)
-
- Levitov's translation of the above in better English: "the one way for
- helping a person who needs it, is to know one of the ones who do treat
- one".
-
- Need I say more? Does anyone still believe that Levitov's translations are
- worth anything?
-
- As an exercise, here is the last sentence on p.31, with its word-for-word
- translation by Levitov. I leave you to work it out, and to figure out what
- it might possibly mean. Good luck!
-
- tvieT nwn anvit fadan van aleC
-
- tvieT = do the ways
- nwn = not who does (but Levitov adds a letter to make it "nwen")
- anvit = one knows
- fadan = one for help
- van = one will
- aleC = each ail
-
- ==> cryptology/swiss.colony.p <==
- What are the 1987 Swiss Colony ciphers?
-
- ==> cryptology/swiss.colony.s <==
- Did anyone solve the 1987 'Crypto-gift' contest that was run by
- Swiss Colony? My friend and I worked on it for 4 months, but
- didn't get anywhere. My friend solved the 1986 puzzle in
- about a week and won $1000. I fear that we missed some clue that
- makes it incredibly easy to solve. I'm including the code, clues
- and a few notes for those of you so inclined to give it a shot.
-
- 197,333,318,511,824,
- 864,864,457,197,333,
- 824,769,372,769,864,
- 865,457,153,824,511,223,845,318,
- 489,953,234,769,703,489,845,703,
- 372,216,457,509,333,153,845,333,
- 511,864,621,611,769,707,153,333,
- 703,197,845,769,372,621,223,333,
- 197,845,489,953,223,769,216,223,
- 769,769,457,153,824,511,372,223,
- 769,824,824,216,865,845,153,769,
- 333,704,511,457,153,333,824,333,
- 953,372,621,234,953,234,865,703,
- 318,223,333,489,944,153,824,769,
- 318,457,234,845,318,223,372,769,
- 216,894,153,333,511,611,
- 769,704,511,153,372,621,
- 197,894,894,153,333,953,
- 234,845,318,223
-
- CHRIS IS BACK WITH GOLD FOR YOU
- HIS RHYMES CONTAIN THE SECRET.
- YOU SCOUTS WHO'VE EARNED YOUR MERIT BADGE
- WILL QUICKLY LEARN TO READ IT.
- SO WHEN YOUR CHRISTMAS HAM'S ALL GONE
- AND YOU'RE READY FOR THE TUSSLE,
- BALL UP YOUR HAND INTO A FIST
- AND SHOW OUR MOUSE YOUR MUSCLE.
- PLEASE READ THESE CLUES WE LEAVE TO YOU
- BOTH FINE ONES AND THE COARSE;
- IF CARE IS USED TO HEED THEM ALL
- YOU'LL SUFFER NO REMORSE.
-
- Notes:
- The puzzle comes as a jigsaw that when assembled has the list of
- numbers. They are arranged as indicated on the puzzle, with commas.
- The lower right corner has a drawing of 'Secret Agent Chris Mouse'.
- He holds a box under his arm which looks like the box
- the puzzle comes in. The upper left
- corner has the words 'NEW 1987 $50,000 Puzzle'. The lower
- left corner is empty. The clues are printed on the
- entry form in upper case, with the punctuation as shown.
-
- Ed Rupp
- ...!ut-sally!oakhill!ed
- Motorola, Inc., Austin Tx.
-
-
-
- ==> decision/allais.p <==
- The Allais Paradox involves the choice between two alternatives:
-
- A. 89% chance of an unknown amount
- 10% chance of $1 million
- 1% chance of $1 million
- B. 89% chance of an unknown amount (the same amount as in A)
- 10% chance of $2.5 million
- 1% chance of nothing
-
- What is the rational choice? Does this choice remain the same if the
- unknown amount is $1 million? If it is nothing?
-
- ==> decision/allais.s <==
- This is "Allais' Paradox".
-
- Which choice is rational depends upon the subjective value of money.
- Many people are risk averse, and prefer the better chance of $1
- million of option A. This choice is firm when the unknown amount is
- $1 million, but seems to waver as the amount falls to nothing. In the
- latter case, the risk averse person favors B because there is not much
- difference between 10% and 11%, but there is a big difference between
- $1 million and $2.5 million.
-
- Thus the choice between A and B depends upon the unknown amount, even
- though it is the same unknown amount independent of the choice. This
- violates the "independence axiom" that rational choice between two
- alternatives should depend only upon how those two alternatives
- differ.
-
- However, if the amounts involved in the problem are reduced to tens of
- dollars instead of millions of dollars, people's behavior tends to
- fall back in line with the axioms of rational choice. People tend to
- choose option B regardless of the unknown amount. Perhaps when
- presented with such huge numbers, people begin to calculate
- qualitatively. For example, if the unknown amount is $1 million the
- options are:
-
- A. a fortune, guaranteed
- B. a fortune, almost guaranteed
- a tiny chance of nothing
-
- Then the choice of A is rational. However, if the unknown amount is
- nothing, the options are:
-
- A. small chance of a fortune ($1 million)
- large chance of nothing
- B. small chance of a larger fortune ($2.5 million)
- large chance of nothing
-
- In this case, the choice of B is rational. The Allais Paradox then
- results from the limited ability to rationally calculate with such
- unusual quantities. The brain is not a calculator and rational
- calculations may rely on things like training, experience, and
- analogy, none of which would be help in this case. This hypothesis
- could be tested by studying the correlation between paradoxical
- behavior and "unusualness" of the amounts involved.
-
- If this explanation is correct, then the Paradox amounts to little
- more than the observation that the brain is an imperfect rational
- engine.
-
- ==> decision/division.p <==
- N-Person Fair Division
-
- If two people want to divide a pie but do not trust each other, they can
- still ensure that each gets a fair share by using the technique that one
- person cuts and the other person chooses. Generalize this technique
- to more than two people. Take care to ensure that no one can be cheated
- by a coalition of the others.
-
-
- ==> decision/division.s <==
- N-Person Fair Division
-
- Number the people from 1 to N. Person 1 cuts off a piece of the pie.
- Person 2 can either diminish the size of the cut off piece or pass.
- The same for persons 3 through N. The last person to touch the piece
- must take it and is removed from the process. Repeat this procedure
- with the remaining N - 1 people, until everyone has a piece.
- (cf. Luce and Raiffa, "Games and Decisions", Wiley, 1957, p. 366)
-
- There is a cute result in combinatorics called the Marriage Theorem.
- A village has n men and n women, such that for all 0 < k <= n and for any
- set of k men there are at least k women, each of whom is in love with at least
- one of the k men. All of the men are in love with all of the women :-}.
- The theorem asserts that there is a way to arrange the village into n
- monogamous couplings.
-
- The Marriage Theorem can be applied to the Fair Pie-Cutting Problem.
-
- One player cuts the pie into n pieces. Each of the players labels
- some non-null subset of the pieces as acceptable to him. For reasons
- given below he should "accept" each piece of size > 1/n, not just the
- best piece(s). The pie-cutter is required to "accept" all of the pieces.
-
- Given a set S of players let S' denote the set of pie-pieces
- acceptable to at least one player in S. Let t be the size of the largest
- set (T) of players satisfying |T| > |T'|. If there is no such set, the
- Marriage Theorem can be applied directly. Since the pie-cutter accepts
- every piece we know that t < n.
-
- Choose |T| - |T'| pieces at random from outside T', glue them
- together with the pieces in T' and let the players in T repeat the game
- with this smaller (t/n)-size pie. This is fair since they all rejected
- the other n-t pieces, so they believe this pie is larger than t/n.
-
- The remaining n-t players can each be assigned one of the remaining
- n-t pie-pieces without further ado due to the Marriage Theorem. (Otherwise
- the set T above was not maximal.)
-
- ==> decision/dowry.p <==
- Sultan's Dowry
-
- A sultan has granted a commoner a chance to marry one of his hundred
- daughters. The commoner will be presented the daughters one at a time.
- When a daughter is presented, the commoner will be told the daughter's
- dowry. The commoner has only one chance to accept or reject each
- daughter; he cannot return to a previously rejected daughter.
- The sultan's catch is that the commoner may only marry the daughter with
- the highest dowry. What is the commoner's best strategy assuming
- he knows nothing about the distribution of dowries?
-
-
- ==> decision/dowry.s <==
- Solution
-
- Since the commoner knows nothing about the distribution of the dowries,
- the best strategy is to wait until a certain number of daughters have
- been presented then pick the highest dowry thereafter. The exact number to
- skip is determined by the condition that the odds that the highest dowry
- has already been seen is just greater than the odds that it remains to be
- seen AND THAT IF IT IS SEEN IT WILL BE PICKED. This amounts to finding the
- smallest x such that:
- x/n > x/n * (1/(x+1) + ... + 1/(n-1)).
- Working out the math for n=100 and calculating the probability gives:
- The commoner should wait until he has seen 37 of the daughters,
- then pick the first daughter with a dowry that is bigger than any
- preceding dowry. With this strategy, his odds of choosing the daughter
- with the highest dowry are surprisingly high: about 37%.
- (cf. F. Mosteller, "Fifty Challenging Problems in Probability with Solutions",
- Addison-Wesley, 1965, #47; "Mathematical Plums", edited by Ross Honsberger,
- pp. 104-110)
-
- ==> decision/envelope.p <==
- Someone has prepared two envelopes containing money. One contains twice as
- much money as the other. You have decided to pick one envelope, but then the
- following argument occurs to you: Suppose my chosen envelope contains $X,
- then the other envelope either contains $X/2 or $2X. Both cases are
- equally likely, so my expectation if I take the other envelope is
- .5 * $X/2 + .5 * $2X = $1.25X, which is higher than my current $X, so I
- should change my mind and take the other envelope. But then I can apply the
- argument all over again. Something is wrong here! Where did I go wrong?
-
- In a variant of this problem, you are allowed to peek into the envelope
- you chose before finally settling on it. Suppose that when you peek you
- see $100. Should you switch now?
-
- ==> decision/envelope.s <==
- Let's follow the argument carefully, substituting real numbers for
- variables, to see where we went wrong. In the following, we will assume
- the envelopes contain $100 and $200. We will consider the two equally
- likely cases separately, then average the results.
-
- First, take the case that X=$100.
-
- "I have $100 in my hand. If I exchange I get $200. The value of the exchange
- is $200. The value from not exchanging is $100. Therefore, I gain $100
- by exchanging."
-
- Second, take the case that X=$200.
-
- "I have $200 in my hand. If I exchange I get $100. The value of the exchange
- is $100. The value from not exchanging is $200. Therefore, I lose $100
- by exchanging."
-
- Now, averaging the two cases, I see that the expected gain is zero.
-
- So where is the slip up? In one case, switching gets X/2 ($100), in the
- other case, switching gets 2X ($200), but X is different in the two
- cases, and I can't simply average the two different X's to get 1.25X.
- I can average the two numbers ($100 and $200) to get $150, the expected
- value of switching, which is also the expected value of not switching,
- but I cannot under any circumstances average X/2 and 2X.
-
- This is a classic case of confusing variables with constants.
-
- OK, so let's consider the case in which I looked into the envelope and
- found that it contained $100. This pins down what X is: a constant.
-
- Now the argument is that the odds of $50 is .5 and the odds of $200
- is .5, so the expected value of switching is $125, so we should switch.
- However, the only way the odds of $50 could be .5 and the odds of $200
- could be .5 is if all integer values are equally likely. But any
- probability distribution that is finite and equal for all integers
- would sum to infinity, not one as it must to be a probability distribution.
- Thus, the assumption of equal likelihood for all integer values is
- self-contradictory, and leads to the invalid proof that you should
- always switch. This is reminiscent of the plethora of proofs that 0=1;
- they always involve some illegitimate assumption, such as the validity
- of division by zero.
-
- Limiting the maximum value in the envelopes removes the self-contradiction
- and the argument for switching. Let's see how this works.
-
- Suppose all amounts up to $1 trillion were equally likely to be
- found in the first envelope, and all amounts beyond that would never
- appear. Then for small amounts one should indeed switch, but not for
- amounts above $500 billion. The strategy of always switching would pay
- off for most reasonable amounts but would lead to disastrous losses for
- large amounts, and the two would balance each other out.
-