Libre said:
Peder - I don't know the barber's paradox. I'm interested. The example I wrote, is the 2 part Epimenides paradox. The regular Epimenides paradox is the 1 part form: This sentence is false.
The 2 part form is even more intriguing, to me, because neither part has anything wrong with it, but put the 2 together, and you get a paradox.
Hofstadter illustrates another such, several step paradox:
A is bigger tha n B; B is bigger than C; C is bigger than A.
Clearly, every part of this train is perfectly ordinary and possible, yet, taken as a whole, it is an impossibility.
I love this stuff.
Libre,
Well, I have had that coffe and it was great!
And I have looked at the book and it was much more and totally different than anything I ever expected. In a sense I am sorry I did (a happy sorry, that is
), because now I have to figure out how to describe something that is totally undescribable. Hofstadter, Jr, would appreciate that!
There are two parts to the description, I suppose. One would be a description of the book (the hard part) and the second would be my reaction to it (the easier part).
I guess the best way to start to describe the book is to compare it to a large encyclopedia. GEB covers an enormous scope and certainly touches on almost every logical, or computational, or mentally gymnastic topic that I have ever heard about in my life, plus 100 times as much more! (Except, oddly it doen't seem to mention the barber's paradox.) Different from an encyclopedia, however, I feel that the author (who is no doubt brilliant) only skims over the surface of his topics, where an encyclopedia would present each explanation in a manner that was satsifyingly complete in some sense.
As a result, GEB has the feel to me of a magician who might say "See now, the way you produce a rabbit is to rub your fingers together and, lo, there is the rabbit! And now that you understand that ......" At which point I say "Whoa! I
don't understand that! And moreover when I do rub my fingers together I don't make a rabbit."
Or to put it another way, it is like trying to drink from a firehose.
Or yet a third way. Sometimes I think the purpose of the author is to dazzle, whereas the purpose of an encyclopedia is to inform.
On a personal level, I am suspicious of the book, is the only word I can use. In disussing rules of the Propositional Calculus, the author points out Contraposition, using its usual name, but then also has a rule he calls Switcheroo, after having renamed it from its usual name. An author who is that flippant with respect to serious material raises my supicions about how much more flippancy there is which is hiding serious content. He might have called
modus ponens exactly that and not lost his audience, I don't think. Especially since it is the most basic deductive principle there is.
His Phantasy View is likewise not necessary, IMO, and only clouds the matter, again IMO. I don't think that it helps to have to say "Now, you have to remember that not all the formula fragments are true, only the last one." as he more or less does when discussing Left and Right brackets. Having to remember what is true defeats the purpose IMO, which is precisely to sort out what is true and what is not. Proceeding only from true formula to true formula in the conventional completely deductive manner may not be as quick but it seems clearer to me. Or maybe I miss the point.
Re "A greater than B, and B greater than C, implies that A is greater than C," is ordinary transitivity and a true statement. However, I suspect that the complete statement really also includes the preliminary statement somewhere that "For three
distinct integers (or reals) A, B and C..." As a result, A greater than A is never allowed as a true statement, and the substitution of A for C in the conclusion 'A is greater than C' is also not allowed. (Unless one is using the weak inequality A is greater than or equal to A. Either way no paradox arises.)
But by now you can tell the book irritates me.
However, just to prove that he didn't conquer me, here by derivation, and not from memory, is his sequence:
1, 3, 7, 12, 18, 26, 35, 45, 56, 69
Short form: it is just too much of a book for me to tackle and in the wrong style for my taste,
Sorry,
Peder