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As stated in an earlier post, things experienced thru our senses are a priori (conceived beforehand, self evident) - my understanding is they need no proof - however by way of comparison, I liken "proof" of a priori to the mere fact it is experienced by the senses. That is what I meant in last post by handing you the chair. We both came to know the chair in the same time and place thru our senses. It is true to us both a priori. But the synthetic a priori, while based upon truths derived a priori, can not be concluded true in the same physical manner, but rather by intellect alone, and therefore, can not be "proved" with our physical senses, yet are true none the less. Campred to Godel statement: If I have it straight, not all true statements in a theory can be proved true by the axioms in the theory, thus conclusion is the theory is incomplete. My analogy to the above is that - the staments in a theory that are proved true by the theory itself, are similar (in theory) to real a priori - i.e. their truth was "self" evident ("self" being the theory). However, true statements that can not be proved by the axioms, I am likening to synthetic a priori. Hope that clears it up.
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Where did everyone go? |
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. |
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I'm not a mathematician but I know a little about communications. The issue seems to be about the differences between the abstract and the concrete. I don't want to get into a discussion about archtypes. It might be simpler to note that perception of data and meaning is individual and that is called Dialogism. Meanwhile, mathematics, other forms of logic and many forms of communications assume that data and meaning are all experientially the same and that is called Monologism. The latter can be more precise, by manner of it's assumptions about meaning, however, the former is more accurate because it takes into consideration a range of observations that has a higher fidelity with perceptions of reality.
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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau |
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ETA: added the omitted if. Last edited by Ken G; 05-November-2009 at 08:12 PM.. |
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Where did everyone go? |
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Despite what you have said elsewhere, the inconsistency of a set of axioms renders it completely useless. There is no recovery. There are proofs of the consistency of ordinary arithmetic. What Godel proved is than any set of axioms that is sufficiently rich to admit the natural numbers is either inconsistent or does not admit a proof withiin that set of axioms of its own consistency. That does not rule out proofs of the consistency of the original set of axioms in some other, possible larger and stronger, set of axioms. So, for instance Peano arithmetic is provable within Zermelo Fraenkel set theory, or using transfinite methods as in Gentzen's proof. If the axioms of arithmetic were inconsistent the result would be catastrophic for mathematics and for those disciplines that rely upon it. For instance, the statement 1+1=2 would be false (and true ). |
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On the other hand, if the axioms of arithmetic are inconsistent then the Godel sentence is both true and false, as is every other sentence that can be formulated. So in either case the Godel sentence is true. |
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If you are right, that Godel can add the axiom (call it A1) "the Peano axioms are consistent" to the Peano axioms, and then use the new set of axioms to prove the Godel statement, then the Godel statement is a false arithmetic expression in the new system, and the new system Peano + A1 is inconsistent. But all we did was axiomatize the assumption that the Peano system is consistent, and we render the resulting system inconsistent! Clearly, it is essential that we not know that the Peano system is consistent if we are to have any hope that it actually is. Quote:
Now you see why it is so important to maintain a difference between actual truth and provable (logical) truth! If we do not make that distinction, then any assumption that arithmetic is consistent (adding axiom A1) will render it inconsistent. It is only by maintaining the distinction I refer to above that we can use the Peano axioms without A1, and be saved from inconsistency by our own sincere uncertainty about whether A1 is a valid axiom. If we do not recognize that distinction, then your argument goes through, with the disastrous result that we know the Godel statement is true, so we have proven the Godel statement, so arithmetic is inconsistent.
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. |
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If you add your A1 ("arithmetic is consistent") to the system that Godel showed to be incomplete, then would we not have to address that new and different system? In fact such a system will have its own Godel sentence.
As before, all I can say is that there is an extensive literature. |
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And yes, sometimes it's an uphill battle! Hang it there...
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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given. If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020. |
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. |
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Secondly, if you attach A1 to the Peano axioms, you will indeed have a new Godel statement, but the relationship of the axioms to that Godel statement will be quite different-- those axioms are inconsistent (as I showed), so the Godel statement is now provable. That axiom set is thus irrelevant to the Peano axioms. Quote:
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. |
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It would not be a regress of incomplete systems-- the very first time we put in the axiom "the Godel statement is true in this system" (or "this system is consistent", or "this system is incomplete", it all amounts to the same end), we no longer have incomplete systems. We have inconsistent systems. This is also why the Godel proof is not an incompleteness theorem, despite the proclivity for hopeful (but naive) mathematicians to call it that. There is no problem with hoping that the system is incomplete, the problem is with claiming you know it is incomplete, which if true, renders it inconsistent and complete.
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As you have recognized elsewhere, any set of axioms that is inconsistent has the property that every sentence that can be formulated is both true and false. That is simply an untenable state of affairs. No such set set of axioms could possibly be "quite useful", or in fact of any use whatever. In that situation 1+1=2 and also 1+1=7. Perhaps that would serve your purposes, but it would not serve the purpose of most others. You were not "right then". You are not "right now". You are simply oblivious. Whether or not one is aware of the inconsistency is completely irrelevant. Lack of awareness, simply sticking your head in the sand, does not cure the problem. It is no more a cure than ignorance of one's cancer is an assurance of prolonged life. This point is too ridiculous for any further debate. We've been through this before and there is simply no educating you. Quote:
On the other hand if the axioms are consistent, then adding a statement that they are consistent adds nothing. So in either case you have demonstrated nothing except a lack of understanding. Quote:
I am not going to debate this further. There is no point, But it is important that there be a counter point to your assertions, which are , most assuredly, ATM. |
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Form the Godel statement G in the system Peano + A1. Prove (from its axioms) that PA1 is consistent, so if G does not have a true meaning, then G cannot be proven. But G asserts that it cannot be proven, so if G does not have a true meaning, then it has a true meaning. The system PA1 is therefore inconsistent. Now, instead of complaining about how "absurd" this is, find a flaw in the proof, or admit that you cannot. Quote:
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. Last edited by Ken G; 06-November-2009 at 05:09 PM.. |
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There is clearly no form of words that I can supply that will persuade Ken G that Godel's theorem is an Incompleteness Theorem
I could continue to say that it is called that because we assume that arithmetic is consistent, not because it proves arithmetic consistent, but it is now clear that this would never be persuasive. |
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1) wrong 2) ATM 3) saying something totally different from anything I've actually ever said, or 4) consistently saying exactly the same thing and proving its truth, only to have you begrudgingly accept that truth and somehow claim that it wasn't what I've been saying and wouldn't even "persuade" me if it came from you instead of me. Sheesh.
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Logic is the grammar of truth. Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible. The only thing intelligence is capable of is recognizing itself. |
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As to 3, you have consistently misunderstood the Godel theorem and basic logic. As to 4 you, have not proved anything of import. |
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Note that the proof of the first Gödel theorem involves a proof of the truth of the Gödel sentence, but not within the limitations imposed. That is in fact precisely what the first Gödel theorem is. The second Gödel incompleteness theorem states that it is impossible to prove completeness of a set of axioms Gödel's first and second theorems are accepted by nearly all mathematicians as an incompleteness theorem, and here is why: 1) The case in which the axioms are inconsistent is completely uninteresting. If any set of axioms is inconsistent, then within that set of axioms all possible sentences are both true and false. That is a totally useless situation, and no one is willing to work with inconsistent axioms. Your protestations to the contrary are just plain ludicrous. 2) It is an accident of semantics that "inconsistent" is commonly taken to include "complete". In point of fact that it a trivial thing. Once it is recognized that a set of axioms is inconsistent, it does not matter one whit whether you also call it consistent or inconsistent. They are utterly useless nevertheless and any and all theorems related to those axioms are worthless -- since all possible theorems are both true and false. Hence there is nothing of importance lost if one simply states that "the fundamental axioms of arithmetic are incomplete", except of course the trivial semantic point that you keep bringing up. Note also that that if one could prove the consistency of a set of axioms using only those axioms it would not be a useful theorem. That is because is is not only possible, but a requirement, that an inconsistent set of axioms be able to prove its own consistency (and also its own inconsistency since all sentences are both true and false). |
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Actually, what I proved was Godel's second theorem. So that is neither 1 nor 2. How can you be a mathematician and not see that?
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A fine discussion of the relation between truth and logic is at http://plato.stanford.edu/entries/ka...ity/#KanAnsHum From this examination of the views of Kant and Hume on the nature of causality and time, it can be suggested that Godel lacked necessary axioms to explain the relation between truth and logic, by neglecting the function of reason as seeing the necessary conditions of experience. In this post I respond to comments from Ken G at Truth and Logic
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No, you did not prove Gödel's second theorem. Neither have you proved Gödel's first theorem. In fact you have not offered anything in this thread that would begin to be accepted as a mathematical proof of anything. BTW Gödel's second theorem states that any consistent set of axioms sufficiently rich as to admit the natural numbers does not admit a proof of its own consistency. You most certainly have not produced a proof of that statement. The fact that you think that you have is merely one more in a long line of demonstrations that you don't understand the problem. |
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Surely inconsistency with reality is ruled out by logic? Observation of the universe shows that the structure of elements is determined by the natural number of protons and neutrons in the nucleus of the atom. Counting the particles gives the periodic table. Hence for a mathematics that describes the universe, the natural numbers are embedded in the structure of matter. How could a true logic possibly be inconsistent with the natural counting of the elements? |
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I don't know what you mean by "Gödel's question". There is nothing that goes by that name in mathematics.
In mathematics "real" has a specific meaning, and it is quite different from that of common usage. In that mathematical context, the natural numbers are a subset of the real numbers and therefore are real. However, "real" in this context is not "real" in the philosophical context or the "real" of general usage (which to me agree with the philosophical meaning). I think you are asking a question with regard to the Platonic view of mathematical objects. In that case I think it is fair to say that most mathematicians view mathematical "truths", numbers, and constructions as being "real" (in the sense of everyday language) and therefore as being things that mathematicians discover as opposed to things that they invent. But this is really a personal philosophic stance, and has no real bearing on the formal structure of mathematics. It is rather akin to the philosophical stance taken by many of the better theoretical physicists, which is that nature is described by some (as yet unknown) set of mathematical laws and it is up to them to discover those laws. That may or may not be "correct" but it does serve the researcher well as a motivational factor in his research. Quote:
Hence inconsistency with "reality" is not a consideration within the formal structure of mathematics. "Reality" in the sense of the physical world is not a part of formal mathematics. However, as a matter of day-to-day pursuit of mathematics as a research subject, it is fair to say that a mathematician would take as an indication that it is not true, the fact that some conjecture would be contradictory to a mathematical relation that is known to be physically applicable and accurate. This is a purely heuristic and motivational statement, however, and again not any part of formal mathematics. In that vein is perhaps valuable to note that correct mathematical theorems are usually "guessed" and once guessed, then proved using the rigorous methods of proof governed by mathematical logic. Mathematics as a research topic is not the deductive monolithic structure that is often perceived by non-mathematicians. Unfortunately what is published and shown to the non-specialist is the polished, and streamlined, final form of the proof a theorem and not the inductive steps, false starts, and illuminating examples that led to the theorem in the first place. Quote:
The logic used by working mathematicians is basically the same logic used by others, though perhaps not so formal and restricted as that considered by logicians (working mathematicians do not restrict themselves to first order logic for instance). The natural numbers, the counting numbers, are a result of the basic axioms of mathematics. That could be the Peano Axioms or the more formal Zermelo Fraenkel axioms (usually with the axiom of choice added). In any case, with the exception of logicians who explore the ramifications of formal axiomatic systems in a rather abstract way, all mathematicians work with a set of axioms that admits the natural numbers and ordinary arithmetic. So essentially all of mathematics is based on the natural numbers in a rather direct manner. I am aware of no mathematics that does not admit the natural numbers, and cannot imagine any such set of axioms that would be of interest to the professional mathematical community or be taken seriously. In mathematics, as in all disciplines, there is a factor of "taste" and without the natural numbers mathematics would be at best tasteless, and frankly completely uninteresting (and useless to those who apply mathematics). |
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