Maze1125 said:
That is not what we are doing.
What we are doing is attempting to apply the phrase "The smallest natural number that cannot be unambiguously described in fourteen words or less." and showing this results in a contradiction and thereby concluding that the phrase "The smallest natural number that cannot be unambiguously described in fourteen words or less." cannot apply to that number.
We are never ever ever trying to apply the phrase to more than one number at once, so the fact that it cannot be applied to more then one number at once is never a problem.
Please try and read over the proof again, because as far as I can tell you're so set on the idea that I'm wrong, and the specific reason that you think I've got wrong, that you're not actually reading what I'm saying.
Yes, it's quite possible there is a flaw, but that is not it.
That's not true at all. In fact, the proof that induction works on the natural numbers is a deductive one.
So, if I'm to understand the proof given a second (more careful) reading, it states in effect:
Value n is the LARGEST natural number that CAN be described, unambiguously in 14 worsd or less.
Value n + 1 is the first (and smallest) natural number that does NOT meet the criteria of being a natural number unambigiously described in 14 words or less.
This value, n + 1 can however be described as "the smallest. . . resulting in a contradiction as the description now applied is shorter than 14 words.
As this logic can hold true for all values of n where the given criteria is met it can be concluded that all natural numbers MUST have a description shorter than 14 words that is non-ambiguous.
Assuming THIS is indeed correct, the proof still demonstrates a logical fallacy.
We are given a condition with two concievable outcomes - true or false. This inductive proof essentially states because the condition is true, it is false; therefore the condition is false for all false.
The logical flaw is not hidden the the mathematical process of the proof itself but rather than the LANGUAGE of the statement. The phrase "the smallest natural number that cannot be unambiguously described in fourteen words or less" is a sentence that makes a statement about itself. Any time a sentence does this it runs the risk of being logically inconsistant.
In effect, the sentence refers to itself because the sentence makes a claim about the description of a number while itself being a description of a number.
The logical flaw is simply this: when you try to apply any value to this sentence, the sentance states in effect that it does not apply to this value. Therefore, the sentence cannot possibly be self-consistently asserted about any number.
The flaw in your proof lies here:
If it can't be then, as every previous natural number can be, this is the smallest natural number that can't be, therefore the phrase "The smallest natural number that cannot be unambiguously described in fourteen words or less." unambiguously describes n+1 in fourteen words. This is a contradiction.
Hence, as the other option results in contradiction, n+1 must be able to be unambiguously described in fourteen words or less.
Because your descriptive sentence is not consistant with respect to itself, it is assumed that the mathematical nature of n is in fact in contradiction. This is very similar to the "Liar's paradox" of "this sentence is false". The sentence itself is a paradox because it is self referential and contradictary.
Because you begin with a statement that cannot apply to any value of n does not imply that this value of N does not exist. This value of N certainly does exist, but when you attempt to apply a description that states in effect "this description does not EVER apply" you obviously run into a problem.
EDIT:
After a bit of snooping about on the internet, I dug up a note that describes this flaw better than I can:
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It is very difficult to pin down this fallacy. It has more to do with the informal nature of the English language, and the paradoxes that can arise from this, than with any mathematical error.
Any sentence that tries to make claims about itself runs the risk of being logically inconsistent. The classic example is the liar's paradox "this sentence is false".
The problem in this case is the following phrase (let's call it S):
the smallest natural number that cannot be unambiguously described in fourteen words or less.
S refers to itself (because it makes claims about descriptions of numbers, and S is such a description). Moreover, it does so in a logically inconsistent fashion: if you try to apply the description S to a number, then it ends up stating that S does not apply to that number.
This means that S cannot be considered as a self-consistent description of any natural number. This, however, does not mean that the number n (in the proof) does not exist! There is such a number n, and n is the smallest natural number that cannot be unambiguously described in fourteen words or less; it's just that the phrase "the smallest natural number that cannot be unambiguously described in fourteen words or less" is not a description of it (in the sense that is being used in the proof), because it is a phrase that cannot be self-consistently asserted about any number.
Therefore, step 4 of the proof (which mistakes the self-inconsistent nature of S with a mathematical contradiction arising from the existence of n) is at fault.
This is also related to Russell's Paradox in set theory: there is no such thing as the "set of all sets" (if there were, you could look at "the set of all sets that do not contain themselves". Let S be this set. Does S contain itself, or not? Either way leads to a contradiction).
Finally, although this particular proof is fallacious, it illustrates a common proof technique which, when used correctly, is very powerful: the well-ordering principle.
If you want to show that something is true for all natural numbers n, one way to do it (which is mathematicall equivalent to a proof by induction but is sometimes more convenient than it) is to reason as follows:
Suppose it's not the case that the statement in question is true for all n. Then there is a smallest n for which it fails. But this leads to a contradiction because . . . . Therefore, it must indeed be the case that the statement in question is true for all n.
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Proofs that follow this pattern are using the well-ordering principle (which says that any non-empty set of natural numbers must have a smallest element), and this is a very common and powerful pattern of proof. When used correctly, that is.
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