[net.misc] ravings on Smullyan and Logical Equivalence

cbostrum (08/02/82)

    From utzoo!decvax!harpo!npoiv!alice!rhm Sat Jul 31 15:37:18 1982
    Are we really going to get bits and pieces of Smullyan's book plastered
    all over the net?
    No, the two statements are not logically equivalent, by any possible
    interpretation that does not include a screenful of caveats.
    This is just one of many levels of errors in Smullyan's book.
    He took a course in logic once but cut the first three classes (so it seems)
    and then wrote a book about it.
    
For people who dont know, referred to is Raymond Smullyan, and one of his
books, "What Is The Name of This Book?", a popularisation of some "cute" 
aspects of "modern logic".
Actually, Raymond Smullyan is a mathematical logician by trade. To say he
"took a course in logic once" is ridiculous nonsense. 
As well as the above book, he has written "Theory of Formal Systems",
published by Princeton University Press in 1961, and "First-Order Logic",
published by Springer Verlag in 1968, and perhaps more but I dont know 
for sure. I have also seen papers by him in the Journal Of Symbolic Logic.
(He has written other "popular" books too: "The Tao is Silent", and
"This Book Needs No Title". Shame, shame)

I would agree that the statement "there are errors in Smullyans book"
but I suspect for totally different reasons. Pray tell, I would love to
know what rhm's reasons are.

Besides, the fact that the "good food" thing was mentioned in Smullyans book
does not make it valueless at all. Doubtless it has occurred other places;
why complain so about "bits and pieces of Smullyans book".
Is this a personal attack against the man??

And the statements arent logically equivalent without a page of caveats?
Come now. You might get me to agree to this, but then you would have no two
english statements being logically equivalent with the same amount of hedging.

I am interested in what people think about the logical equivalence of
the two debated sentences, and what people think about logical
equivalence and deciding when it holds, in general.
Remember, they were: "Good food is not cheap" and "Cheap food is not good".

rhm (08/02/82)

I don't know Smullyan - I do know his book.
The first few lectures in a logic course stress the importance of
quantification.  Without the discipline of quantification, one is left
to make some decision about the meaning of the English word "is".
Inclusion of pontifical statements in a book on logic about the true
meaning of sentences like "Good food is not cheap." simply sets the
study of logic back to the middle ages.
Smullyan's book is a goldmine of incorrectly and insufficiently quantized
sentences.

I still hope that the net does not fill up with bits and pieces of
the rather carelessly formulated problems from Smullyan's book.