Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

I liked this reaction, from KurtG:

Dear Mr T.,

Your problem is very much like I have been considering. Assume that we have a consistent and complete axiomatization of all true first-order logic statements about natural numbers. Then we can build an algorithm that enumerates all these statements. This means that there is an algorithm N(n) that, given a natural number n, computes a true first-order logic statement about natural numbers such that, for all the true statements, there is at least one n such that N(n) yields that statement. Now suppose we want to decide if the algorithm with representation a halts on input i. We know that this statement can be expressed with a first-order logic statement, say H(a, i). Since the axiomatization is complete it follows that either there is an n such that N(n) = H(a, i) or there is an n' such that N(n') = ¬ H(a, i). So if we iterate over all n until we either find H(a, i) or its negation, we will always halt. This means that this gives us an algorithm to decide the halting problem. Since we know that there cannot be such an algorithm, it follows that the assumption that there is a consistent and complete axiomatization of all true first-order logic statements about natural numbers must be false. There is no way your application can be built, and for this advice I am willing to waive any fee. Sincerely, K. Gödel.



"But the other guy says he can build this in Java in 50 days, I think you're not as smart as he is"


The boss is always right




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: