Most Helpful Customer Reviews
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20 of 20 people found the following review helpful:
5.0 out of 5 stars
Good Intro to a DEEP Subject, May 12, 2006
At the time this book was written, Raymond Smullyan was one of the world's leading experts on Godel's Incompleteness Theorems -- some of the deepest mathematical results of the 20th century.
This book is actually a gentle intro to these topics, and the most amazing part of it is that Dr. Smullyan keeps the level suitable for children.
That does NOT mean this book is not suitable for adults. It is extremely entertaining no matter what your age is.
The book is mostly a progression of logical conundrums. You are started out on the island of knights and knaves. These two types of people are visually indistinguishable, but knights always tell the truth while knaves always lie.
You are then presented with various scenarios where the objective is for you to ask one question from which you obtain some meaningful information without knowing whether or not the person you are asking is a knight or a knave. The classic example is that you meet two people one of whom is a knight and one of whom is knave. Your objective? Ask one of them one question that allows you to determine which one is the knight and which one is the knave. Answer? "If I were to ask your friend if he was a knight, would he say 'Yes'" A knight will always answer this question "Yes" and a knave "No". If you can follow the logic through to conclude this, you are on your way!!
The situations through the book grow more complex. For example, later you find yourself on a similar island where the natives no longer speak English. They words for yes and no are "boo" and "da". The problem is, you don't know which is which!
At the end of the book, you are presented with the ultimate level of complexity where not only do half the people always lie and half tell the truth, and not only do they use the words "boo" and "da" for yes and no (without you knowing which is which), but half of the population is also insane which means that whatever is true, they BELIEVE the opposite. So an insane liar always inadvertantly tells the truth because what they believe is false...and then they lie about it.
Sound hard?
Yeah, that's the point.
Nonetheless, the book is a nice progression, and you definitely get better and better and following the logic through and thinking in these terms, which makes this book GREAT mental exercise! Some of the best I have found, in fact.
One final comment, John Houston's review is very wrong on the point of implication: an implication of the form a->b, is ALWAYS true when a is false. This is elementary logic -- a subject in which Dr. Smullyan was a world renowned expert.
I have no doubt that Dr. Houston is a very knowledgeable physicist, but unfortunately -- in spite of his apparently strong feelings to the contrary -- this has not prepared him to comment competently on formal logic.
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8 of 9 people found the following review helpful:
5.0 out of 5 stars
Great Book, July 16, 2004
A true delight to read, although the one reviewers comments (John Morrison from Houston) brought to mind the truth of Pope's comment,"A little learning is a dangerous thing; Drink deep, or taste not the Pierian spring: There shallow draughts intoxicate the brain, And drinking largely sobers us again." As you read this book hopefully your brain will be stimulated to ask questions AND to dig deeper to learn ther answers. Smullyan is NOT wrong when he says that a false hypothesis yields a true conditional statement. I haven't read the book in decades, so I can't comment on whether or not Smullyan explicits says this, but conditional statements do not express causal relations (I can understand how a physicist would think this.)
Anyhow, this is a great book for young children with inquisitive minds and even for old children who think they know it all.MB
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5 of 5 people found the following review helpful:
5.0 out of 5 stars
A Fantastic Logic Puzzle Book, September 8, 1999
By A Customer
Raymond Smullyan introduces the readers to simple logic problems and then starts to grow them more complex. Answers to the puzzles are provided with explaination, but Smullyan's more recent books clearly dig deeper. However, if you want some good knight/knave and dracula puzzles, this is a good place to start to learn about Godel. I recommend also obtaining: "Lady or the Tiger? And Other Logic Puzzles Including a Mathematical Novel That Features Godel's Great Discovery"
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