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        2007-12-18

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Induction... Oversights
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Fundamental... Oversights
Set Theory
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MORE DETAIL ON FUNDAMENTAL... OVERSIGHTS


 

 

SECTIONS

DEFINITION of “PARADOX”... AND HIDDEN “RULES OF DEFERENCE”

DEFINITION of “INCONSISTENCY”

DEFINITION of “DEFINITION”

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!

 

DEFINITION of “PARADOX”...
AND ITS HIDDEN “RULES OF DEFERENCE”

Paradox no longer has a formal mathematical meaning, Cantor’s Paradox to the contrary notwithstanding. For millennia, before Cantor, “paradox” was synonymous with inconsistency” (see formal definition, below), both terms at that time being handled quite informally by today’s standards. But, here at the beginning of the 21st Century, paradox in a mathematical theory is (still, since Cantor) considered acceptable whereas formal inconsistency is not. Examples of standard results from set theory that are considered to be paradoxical but not to make set theory inconsistent are:

  • a0 + 1 = a0

  • that there seem to be the same number of even numbers as numbers since it seems that they can be paired n <-> 2n

  • “paradoxical measure” is considered to be a legitimate area of study in mathematics (measure theory, but the paradox derives from set theory)

  • Cantor held that a0 (the cardinality of the set of all natural numbers Á 4 {1,2,3...}) is the largest cardinality that you can possibly get by the continued process of adding 1s; but Cantor also had the relatively paradoxical concept of transfinite ordinals, and there adding “1s” to the first ordinal (“1st”) eventually gets you not only to the first transfinite ordinal ω, but then to ω + 1 (which is > ω), and then eventually to the transfinite ordinal Ω (which is >>> ω) which has cardinality >>> a0

  •  by the standard theorem concerning the cardinality of set exponentiation, <<< (since the cardinality of the first term is countably infinite, i.e. a0, and a0 is very much less than )

  • if, using the standard axioms and rules of inference of set theory, one subtracts the elements of Á 4 {1,2,3...} 1 at a time, the cardinality remains a0 , even when all the elements have been removed and all that remains is the empty set (hint: finite induction)

This brings up a touchy subject, one that can perhaps best be communicated satirically. To the standard axioms and rules of inference of mathematical theory we must add the hitherto unrecognized...

  • RULES OF DEFERENCE: the DON’T!”s

These RULES OF DEFERENCE turn what would otherwise be “inconsistency” (very bad, and worse, formally unacceptable to mathematicians) into “paradox” (not only acceptable to mathematicians, but even romantic). The first result above a0 + 1 = a0 is “paradoxical” since it seems to imply a mathematically unfortunate consequence, i.e. that 1 = 0, which we would get if we subtracted a0 from both sides of the equation. But set theory dances around the fact that this is formal inconsistency by saying DON’T! subtract that a0 from both sides despite the fact that transfinite arithmetic is derived from finite arithmetic and should share the same rules of inference. (Believe it or not, mathematicians will actually say that we must not do it because we will get an inconsistency; it somehow remains mere “paradox” as long as we DON’T!)

And DON’T! try to relate a0 + 1 = a0 to the fact that if we set subtract {1,2,3...} from e.g. {0,1,2,3...} we get {0} and not the empty set. In fact, set theory has evolved a whole pantheon of DON’T!s that lie totally outside the official formal axioms and rules of inference — or any other formal part — of set theory, there to keep things from slipping into... “inconsistency”.  More on these, later.

The second result is paradoxical for much the same reason, e.g. if we set subtract {2,4,6...} from {1,2,3...}, instead of the empty set we get {1,3,5...}, which is far from empty. But the sets {2,4,6...} and {1,2,3...} seem to have the same number of elements if we go by the  n <-> 2n mapping, so subtracting them should... uhhh... well, anyway, “paradox”, but not formal inconsistency since we DON’T!

The other results follow along those same lines.

Modern mathematics, not just set theory, pretty much depends on putting what is actually fatal inconsistency off to mere “paradox”. And to a theory’s rules of inference we tacitly add RULES OF DEFERENCE, the ever-growing lists of DON’T!s. (See RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!, below.)

 

 

SECTIONS

DEFINITION of “PARADOX”... AND HIDDEN “RULES OF DEFERENCE”

DEFINITION of “INCONSISTENCY”

DEFINITION of “DEFINITION”

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!

 

DEFINITION of “INCONSISTENCY”

First let's go back and look at a standard definition of a “theory”.

  • THEORYA “theory” consists of a set of the axioms (the primitive assumptions, standard by definition), a set of rules of inference (again, standard by definition) , and all the “theorems” (propositions) that can possibly be derived from them.

We need to emphasize this last point in the definition of a “theory” because it is an essential part of what mathematicians overlook when dealing with questions of the inconsistency of set theory. A theorem is still formally a theorem even if mathematicians have failed to recognize it or discover its proof, even if it contradicts a theorem already proven.

An example: if in a finite arithmetic theory (there are several variants, and many more possible) we have a theorem that a = b, and we have the (finite) number c, then a - c = b - c is also a theorem, since we must derive every possible theorem that the rules of inference allow, and in finite arithmetic there is a rule of inference that allows adding or subtracting equal quantities from both sides of an equation (and still getting an equality).

It is actually somewhat easier to define “inconsistency” before “consistency”, and then, if needed, define the latter in terms of the former.

  • INCONSISTENCY A theory is “inconsistent” if it has as theorems both a proposition/theorem and its negation, i.e., for emphasis, if it is even possible to derive both a proposition/theorem and its negation/contradiction from the axioms using the standard rules of inference.

We also need to emphasize with regard to derivation:

  • In all mathematics, the elements of a theory are ostensibly “spacetime independent”. I.e. any axiom, rule of inference, or theorem can be used at any “place-time” in a derivation. Set theory does not stick to this formal requirement, and mathematics does not have adequate arrangements for mathematicians not to stick to it. More on this, later.

We should also note that there are 2 common ways for a theory to be inconsistent:

  • The combination of axioms gives us an inconsistency (under the rules of inference).

  • A single axiom can be inconsistent by itself in what it assumes, making the combination inconsistent (again, under the rules of inference).

This latter shows up in problems associated with the standard Axiom of Infinity.

  • HISTORICAL FACT — PSYCHOLOGY — Imminent mathematicians faced with the derivation of a contradiction in set theory have said things to the effect that “the assumption that you can validly perform that derivation is proven false by the fact that you arrive at a contradiction.”

This is historical fact. Note the... oversight with regard to the standard definition of inconsistency:

  • If a theory is inconsistent, then one must be able — theoretically — to validly derive (both sides of) a contradiction, and any statement to the effect that “the assumption that you can validly perform that derivation is proven false (merely) by the fact that you arrive at a contradiction” is per force a mathematically incompetent statement to make under any circumstances whatsoever.

It would be essential to question/determine whether it was derivable from only the standard axioms using only the standard rules of inference, but — historical fact — these imminent mathematicians did not do so, perhaps because the derivations were so straightforward. The assumption they actually seem to hold as most fundamental is that set theory must be consistent, and therefore any derivation/proof to the contrary is invalid.

 

 

SECTIONS

DEFINITION of “PARADOX”... AND HIDDEN “RULES OF DEFERENCE”

DEFINITION of “INCONSISTENCY”

DEFINITION of “DEFINITION”

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!

 

DEFINITION of “DEFINITION”

It is standardly agreed in mathematics that when a definition is used in a proof, that, in order for the proof to be valid, it is necessary that the proof must remain essentially unchanged semantically when the original definition is substituted for the defined entity. E.g. if we define the set of all natural numbers, Á, as Á 4 {1,2,3...}, in any proof where we use the symbol Á we must be able to substitute not only {1,2,3...}, but its original meaning-definition and so on, until we get to the primitive entities whose existence is postulated in the standard axioms. And when we do so, the essential meaning-semantics of the proof and its stages of derivation must remain unchanged, even though the form(s) may be quite different. (E.g., the proofs tend to get a bit longer.)

  • HISTORICAL FACT — PSYCHOLOGY — Imminent mathematicians faced with the derivation of a contradiction in set theory have said things to the effect that “the derivation of the inconsistency is invalid as it refers to the sequential-serial construction-definition of the entities in question which now have a ‘simultaneous existence’.”

Historical fact — this “simultaneous existence” is not a “to the effect” paraphrase; it is a direct quote, from a context like that paraphrased above.

Note the logical similarity to:

  • “We are out on a limb, and we no longer depend on the tree we climbed to get out on the limb.”

An obvious problem with this new “simultaneous existence” is that if there is a fatal flaw in the original construction, e.g. with regard to later usage, it may remain invisible for quite some time... and has.

 

 

SECTIONS

DEFINITION of “PARADOX”... AND HIDDEN “RULES OF DEFERENCE”

DEFINITION of “INCONSISTENCY”

DEFINITION of “DEFINITION”

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!

 

 

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

Set theory is taken so much for granted that it is no longer a field of specialization in mathematics. We should emphasize that this is transfinite set theory. Finite set theory is taken even more for granted, if that is possible. And the origins of transfinite set theory are the victims of serious... oversights.

  • Transfinite set theory is formally derived from finite arithmetic (the number 1 and its successors, created by cumulatively adding 1), but it is derived in such a way that one cannot substitute the original definitions for the newly defined entities, i.e. it is defined in such a way that the old axioms and rules of inference must be abandoned if one is to maintain even a semblance of theoretical consistency.

Obvious examples:

  • Set theory abandons the standard rule of inference of finite arithmetic that says that equal quantities may be subtracted from both sides of an equation when it arrives at the transfinite arithmetic equation
    a0 + 1 = a0 .

  • Set theory abandons the natural relationship between set subtraction and arithmetic that existed in finite arithmetic; e.g. even though one may set subtract the set {1,2,3...} from {0,1,2,3...} and get {0}, one may not relate that to a falsification of a0 + 1 = a0 since {1,2,3...} and {0,1,2,3...} are formally considered to have the same number of elements (their cardinality).

  • Set theory ignores the remainder of 1 when integer dividing 1 by any transfinite number, even though it acknowledges the quotient of 0.

This last has to do with the fact that Cantor and every leading set theorist up to the beginning of the 21st Century have felt the need to deny the natural existence of infinitesimals, which we might as well call “transfinitesimals”, and implicitly affirm that the Archimedean Axiom cannot be extended to transfinites.

Set theory abandons (some of) its origins for the reasons described above, that if it did not do so, set theory would obviously be inconsistent, since “1 = 0” would be considered too paradoxical to be mere paradox. Unfortunately, as we also saw above, this ploy does not work on several grounds, and set theory remains inconsistent even though we have disguised its inconsistency with an agreement not to apply standard rules of inference in standard ways. Set theory’s excuse has chutzpah:

  • We DON’T! dont subtract a0 from both sides of a0 + 1 = a0
    because, if we did, set theory would be inconsistent!
    (Therefore we DON’T! allow it, even though subtracting equal quantities from both sides of an equation is allowed in the finite arithmetic which is the foundation of set theory and its transfinite arithmetic)

We... oversight the fundamental formal definition of theoretical inconsistency, that if it is even possible to derive a contradiction then the theory is inconsistent. Transfinite arithmetic now has its own “simultaneous existence” and does not need to refer (completely) to its finite origins; indeed it must not do so, because if it does, that will “make” set theory “inconsistent”. As a reminder...

  • “In set theory we are out on a limb, and we no longer depend on the tree we climbed to get out on the limb.”

If mathematics — set theory in particular — is going to insist on proceeding as it has for well over a century, it-we must make formal acknowledgement of the formal role of RULES OF DEFERENCE, the DON’T!s that are so essential, but are not “spacetime/place-time independent” as is formally required in current mathematics.

 

 

SECTIONS

DEFINITION of “PARADOX”... AND HIDDEN “RULES OF DEFERENCE”

DEFINITION of “INCONSISTENCY”

DEFINITION of “DEFINITION”

FINITE ARITHMETIC -> TRANSFINITE SET THEORY

RULES OF DEFERENCE?! WHAT LIES HIDDEN BY THESE... OVERSIGHTS?!

 

RULES OF DEFERENCE?!
WHAT ELSE LIES HIDDEN BY THESE... OVERSIGHTS?!

Unwritten, even unspoken as such, the hidden Rules of Deference, the DON’T!s that are invisibly ubiquitous and so essential to current standard formal theory, but formally disallowed by that same theory, are waiting to be acknowledged by the mathematical community.

The hint of all that lies hidden, of what is in store for mathematics, can be summed up as (repeated here for emphasis):

  • If mathematicians formally or informally  refrain from allowing/accepting as valid any derivations that yield a contradiction, then it is literally impossible for any theory to be (seen by them as) inconsistent.

Think of all the places where derivations are rejected because of... “lack of convergence”, “result undefined”, “contradiction”, etc. Now, think: should (a consistent) theory have produced “convergence”, a “defined result”, whatever...?

Set theory... well, new directions will be needed. But we can all take heart: many, many, many papers will need to be written to transition away from the standard inconsistency of 19th-20th Century set theory. It may even be that “inconsistency” can be co-opted in the new theory — the new theories — that will evolve.

 

This article should have given even an unsympathetic reader at least pause with regard to the possibility of inconsistency in today’s standard set theory. The PAIAS articles on Set Theory and its inconsistency follow up on the above and show how standard inconsistencies derive from the fundamental result in set theory that a0 + 1 = a0 . There are also further problems with the standard Axiom of Infinity.


 

 

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