Customer Reviews

What Is the Name of This Book?: The Riddle of Dracula and Other Logical Puzzles (Penguin Press Science)

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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 yes/no question from which you obtain some meaningful information without knowing whether the person you are asking is a knight or a knave. The obvious example of this, you meet one person on the island, and you want to ask them one yes/no question that allows you to determine whether they are a knight or a knave. Obviously, this would be pretty handy under the circumstances. Can it be done? Yes. Ask them, "If I were to ask you if you were a knight, would you 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!! It's very easy to follow through for the knight, but the knave is a bit more tricky, but this example indicates the importance of case analysis and the use of hypotheticals in your questions to induce lying about lying.

The situations in the book steadily grow more complex. For example, later you find yourself on a similar island where the natives use the words "boo" and "da" for "yes" and "no". 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 tricky?

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.

I will leave it to Dr. Smullyan to discuss to connection of these exercises with Godel's work.

One final comment, an earlier 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 formal logic -- a subject in which Dr. Smullyan was a renowned expert.

Interestingly, this strikes many people as highly objectionable as you will be able to tell from the comments to this review. The crux of the issue is that when I utter a statement of the form p->q, I am not asserting anything about the truth of either p or q. I am only asserting something about the relationship between the two. Namely, I am asserting that whenever p is true, q will be true as well. So the only way I can possibly be wrong about that -- that is, the only way the statement p->q can be false -- is if p is true and q is false.

And that is how we define the truth value of the statement p->q in mathematics: false if p is true and q is false, true in all other cases.

Ultimately, this works well for mathematics because mathematical statements are atemporal. For example, the statement "It is raining outside" might be true at some times, false at others. But that is not a mathematical statement. Mathematical statements like "2+2=5" are either always true or always false and we just have to figure out which.

For domains outside of mathematics, other conventions might be more appropriate...

Regardless, a wonderful book.

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

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"

An amazing book that trains you to use your brain effectively through a careful structure that increases in complexity as you progress. I read it when very young and would like to get copies for all my staff as it is an excellent tutorial on logic and perfect for orienting systems programmers into looking at complex problems with a fresh viewpoint. Sadly it appears to be out of print and I join the cry in asking the publisher to pull it out of the archives.

Don't read it at night as it would make you sleepless. The riddles are repeating themselves much. If you are a logical person, it won't take long to bore you. If you are not, it is a good exercise to train you to think in a logical way. The name of the book is paradoxical but the riddles are not, luckily. Memorize some interesting puzzles and test your friends would make you popular in peer group, I am sure.

I use this book to give puzzle exercises to my University students. Publisher should re-print the book!

This book is a chockful of puzzles and riddles, humorous and bizarre. The author (Raymond Smullyan) uses these puzzles to introduce formal logic in a particularly fun and interesting way. This book also illustrates the unique sense of humor many mathematicians. He characterizes a drunken mathematician as one who says, "I can prove anyshing!"

This was a mind boggling book.
One of my favorites in logic puzzles. Surely fits a brain addicted to Hofstadter, Douglas Adams, (Martin Gardner) and other wizards.

This is a book that parents should buy for their adolescent children (until it becomes compulsory reading at school). It provides both the entertainment of tales and the much needed ability to reason.

Solving the riddles set forth by the author is one of the best investment of their time the readers can do. It will repay many times whatever line of work they end up embarking on. It is also fun.

The beauty of this book that the problems in it do not require any special knowledge. It can almost equally be tackled by old and young. I was 11 or so when I read this book and was able to enjoy many problems ... I still enjoy them when I am 31. Please, reprint the book!