- #1
phoenixthoth
- 1,605
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TUZFC
the general idea is to find a way to axiomatize a universal set into existence in a way that doesn't contradict other axioms.
there are potential ways this might be done, including
1. changing the subsets axiom
2. using ternary logic and changing all axioms
1 would go something like this: there is a set with the usual subset properties UNLESS the existence of that subset leads to a contradiction.
2 would be to use 3 valued or ternary logic. see the two articles here:
http://plato.stanford.edu/entries/logic-fuzzy/
http://plato.stanford.edu/entries/logic-manyvalued/
there isn't a unique way to do fuzzy logic, but let's at least assume that ternary logic generalizes binary logic in the following way:
[tex]\begin{array}{cccccccc}
A & B & \symbol{126}A & A\vee B & A\wedge B & A\rightarrow B &
A\leftrightarrow B & \left( A\wedge \left( A\rightarrow B\right) \right)
\rightarrow B \\
T & T & F & T & T & T & T & T \\
T & M & F & T & M & M & M & M \\
T & F & F & T & F & F & F & T \\
M & T & M & T & M & T & M & T \\
M & M & M & M & M & M & M & M \\
M & F & M & M & F & M & M & M \\
F & T & T & T & F & T & F & T \\
F & M & T & M & F & T & M & T \\
F & F & T & F & F & T & T & T
\end{array}[/tex]
the main observation is that russell's paradox is based on a tautology that isn't a tautology in ternary logic. also note that the standard modus ponens above also fails to be a tautology. however, one may be able to resuce this fact by eliminating ternary logic from all axioms except the subsets axiom in the following way:
in non SS (subsets) axioms, if there is a well formed formula W, and V() is an operator that sends a wff to its truth value, then by replacing appearances of W in the axiom by V(W)=T, we get similar results as the axiom "intends" while still allowing V(W) to be occasionally M. for example, while A<->B if A and B are either both true or both false, V(A<->B)=M if either V(A)=M or V(B)=M. by replacing A<->B with V(A<->B)=T, we get the usual results.
in the case of SS, we can replace it by this:
SS2: [tex]\exists x\forall yV\left( \left( y\in x\leftrightarrow y\in a\wedge A\left( y\right) \right) \right) \neq F[/tex].
this would not contradict the following axiom:
US: [tex]\exists x\forall yV\left( y\in x\right) =T[/tex]
at least by russell's paradox. there may be other ways US contradicts TZFC, ternary-ZFC.
a list of axioms. in TUZFC, versions 2 would be more appropriate:
1. axiom of extensionality:
[tex]\forall x\left( x\in a\leftrightarrow x\in b\right) \rightarrow a=b[/tex]
axiom of extensionality version 2:
[tex]V\left( \forall x\left( V\left( x\in a\leftrightarrow x\in b\right)
=T\right) \rightarrow a=b\right) =T[/tex]
2. axiom of the unordered pair:
[tex]\exists x\forall y\left( y\in x\leftrightarrow y=a\vee y=b\right) [/tex]
axiom of the unordered pair version 2:
[tex]V\left( \exists x\forall y\left( V\left( y\in x\leftrightarrow y=a\vee
y=b\right) =T\right) \right) =T[/tex]
3. axiom of subsets:
[tex]\exists x\forall y\left( y\in x\leftrightarrow y\in a\wedge A\left(
y\right) \right) [/tex]
axiom of subsets version 2:
[tex]V\left( \exists x\forall yV\left( y\in x\leftrightarrow y\in a\wedge
A\left( y\right) \right) =T\right) =T[/tex]
axiom of subsets version 3:
[tex]V\left( \exists x\forall yV\left( \left( y\in x\leftrightarrow y\in a\wedge
A\left( y\right) \right) \right) \neq F\right) =T[/tex]
4. axiom of the sum set:
[tex]\exists x\forall y\left( y\in x\leftrightarrow \exists z\in a\left( y\in
z\right) \right) [/tex]
axiom of the sum set version 2:
[tex]V\left( \exists x\forall y\left( V\left( y\in x\leftrightarrow
\exists z\in a\left( y\in z\right) \right) =T\right) \right) =T[/tex]
5. axiom of the power set:
[tex]\forall x\exists y\left( \forall z\left( z\in y\leftrightarrow z\subset
x\right) \right) [/tex]
axiom of the power set version 2:
[tex]V\left( \forall x\exists y\left( \forall zV\left( z\in
y\leftrightarrow z\subset x\right) =T\right) \right) =T[/tex]
6. axiom of the empty set:
[tex]\exists x\forall y\left( y\notin x\right) [/tex]
axiom of the empty set version 2:
[tex]V[/tex][tex]\left( \exists x\forall yV\left( y\in x\right) =F\right) =T[/tex]
7. axiom of infinity:
[tex]\exists x\left( \O \in x\wedge \forall y\in x\left( y^{\prime }\in x\right)
\right) [/tex]
axiom of infinity version 2:
[tex]V[/tex][tex]\left( \exists x\left( V\left( \O \in x\wedge \forall y\in
x\left( y^{\prime }\in x\right) \right) =T\right) \right) =T[/tex]
8. axiom of the universal set
[tex]V\left( \exists x\forall yV\left( y\in x\right) =T\right) =T[/tex]
9. axiom of replacement:
[tex]\exists x\forall y\in a\left( \exists zA\left( y,z\right) \rightarrow
\exists z\in xA\left( y,z\right) \right) [/tex]
axiom of replacement version 2:
[tex]V\left( \exists x\forall y\in a\left( V\left( \exists zA\left(
y,z\right) \rightarrow \exists z\in xA\left( y,z\right) \right) =T\right)
\right) =T[/tex]
10. axiom of foundation/regularity:
[tex]\exists xA\left( x\right) \rightarrow \exists x\left( A\left( x\right)
\wedge \forall y\in x\left( !A\left( y\right) \right) \right) [/tex]
axiom of foundation/regularity version 2:
[tex]V\left( \exists xA\left( x\right) \rightarrow \exists x\left(
V\left( A\left( x\right) \wedge \forall y\in x\left( !A\left( y\right)
\right) \right) =T\right) \right) =T[/tex]
11. axiom of choice (typo?):
[tex]\forall x\in a\exists A\left( x,y\right) \rightarrow \exists y\forall x\in
aA\left( x,y\left( x\right) \right) [/tex].
axiom of choice version 2:
[tex]V\left( \forall x\in a\exists A\left( x,y\right) \rightarrow
\exists y\forall x\in aA\left( x,y\left( x\right) \right) \right) =T[/tex]
the general idea is to find a way to axiomatize a universal set into existence in a way that doesn't contradict other axioms.
there are potential ways this might be done, including
1. changing the subsets axiom
2. using ternary logic and changing all axioms
1 would go something like this: there is a set with the usual subset properties UNLESS the existence of that subset leads to a contradiction.
2 would be to use 3 valued or ternary logic. see the two articles here:
http://plato.stanford.edu/entries/logic-fuzzy/
http://plato.stanford.edu/entries/logic-manyvalued/
there isn't a unique way to do fuzzy logic, but let's at least assume that ternary logic generalizes binary logic in the following way:
[tex]\begin{array}{cccccccc}
A & B & \symbol{126}A & A\vee B & A\wedge B & A\rightarrow B &
A\leftrightarrow B & \left( A\wedge \left( A\rightarrow B\right) \right)
\rightarrow B \\
T & T & F & T & T & T & T & T \\
T & M & F & T & M & M & M & M \\
T & F & F & T & F & F & F & T \\
M & T & M & T & M & T & M & T \\
M & M & M & M & M & M & M & M \\
M & F & M & M & F & M & M & M \\
F & T & T & T & F & T & F & T \\
F & M & T & M & F & T & M & T \\
F & F & T & F & F & T & T & T
\end{array}[/tex]
the main observation is that russell's paradox is based on a tautology that isn't a tautology in ternary logic. also note that the standard modus ponens above also fails to be a tautology. however, one may be able to resuce this fact by eliminating ternary logic from all axioms except the subsets axiom in the following way:
in non SS (subsets) axioms, if there is a well formed formula W, and V() is an operator that sends a wff to its truth value, then by replacing appearances of W in the axiom by V(W)=T, we get similar results as the axiom "intends" while still allowing V(W) to be occasionally M. for example, while A<->B if A and B are either both true or both false, V(A<->B)=M if either V(A)=M or V(B)=M. by replacing A<->B with V(A<->B)=T, we get the usual results.
in the case of SS, we can replace it by this:
SS2: [tex]\exists x\forall yV\left( \left( y\in x\leftrightarrow y\in a\wedge A\left( y\right) \right) \right) \neq F[/tex].
this would not contradict the following axiom:
US: [tex]\exists x\forall yV\left( y\in x\right) =T[/tex]
at least by russell's paradox. there may be other ways US contradicts TZFC, ternary-ZFC.
a list of axioms. in TUZFC, versions 2 would be more appropriate:
1. axiom of extensionality:
[tex]\forall x\left( x\in a\leftrightarrow x\in b\right) \rightarrow a=b[/tex]
axiom of extensionality version 2:
[tex]V\left( \forall x\left( V\left( x\in a\leftrightarrow x\in b\right)
=T\right) \rightarrow a=b\right) =T[/tex]
2. axiom of the unordered pair:
[tex]\exists x\forall y\left( y\in x\leftrightarrow y=a\vee y=b\right) [/tex]
axiom of the unordered pair version 2:
[tex]V\left( \exists x\forall y\left( V\left( y\in x\leftrightarrow y=a\vee
y=b\right) =T\right) \right) =T[/tex]
3. axiom of subsets:
[tex]\exists x\forall y\left( y\in x\leftrightarrow y\in a\wedge A\left(
y\right) \right) [/tex]
axiom of subsets version 2:
[tex]V\left( \exists x\forall yV\left( y\in x\leftrightarrow y\in a\wedge
A\left( y\right) \right) =T\right) =T[/tex]
axiom of subsets version 3:
[tex]V\left( \exists x\forall yV\left( \left( y\in x\leftrightarrow y\in a\wedge
A\left( y\right) \right) \right) \neq F\right) =T[/tex]
4. axiom of the sum set:
[tex]\exists x\forall y\left( y\in x\leftrightarrow \exists z\in a\left( y\in
z\right) \right) [/tex]
axiom of the sum set version 2:
[tex]V\left( \exists x\forall y\left( V\left( y\in x\leftrightarrow
\exists z\in a\left( y\in z\right) \right) =T\right) \right) =T[/tex]
5. axiom of the power set:
[tex]\forall x\exists y\left( \forall z\left( z\in y\leftrightarrow z\subset
x\right) \right) [/tex]
axiom of the power set version 2:
[tex]V\left( \forall x\exists y\left( \forall zV\left( z\in
y\leftrightarrow z\subset x\right) =T\right) \right) =T[/tex]
6. axiom of the empty set:
[tex]\exists x\forall y\left( y\notin x\right) [/tex]
axiom of the empty set version 2:
[tex]V[/tex][tex]\left( \exists x\forall yV\left( y\in x\right) =F\right) =T[/tex]
7. axiom of infinity:
[tex]\exists x\left( \O \in x\wedge \forall y\in x\left( y^{\prime }\in x\right)
\right) [/tex]
axiom of infinity version 2:
[tex]V[/tex][tex]\left( \exists x\left( V\left( \O \in x\wedge \forall y\in
x\left( y^{\prime }\in x\right) \right) =T\right) \right) =T[/tex]
8. axiom of the universal set
[tex]V\left( \exists x\forall yV\left( y\in x\right) =T\right) =T[/tex]
9. axiom of replacement:
[tex]\exists x\forall y\in a\left( \exists zA\left( y,z\right) \rightarrow
\exists z\in xA\left( y,z\right) \right) [/tex]
axiom of replacement version 2:
[tex]V\left( \exists x\forall y\in a\left( V\left( \exists zA\left(
y,z\right) \rightarrow \exists z\in xA\left( y,z\right) \right) =T\right)
\right) =T[/tex]
10. axiom of foundation/regularity:
[tex]\exists xA\left( x\right) \rightarrow \exists x\left( A\left( x\right)
\wedge \forall y\in x\left( !A\left( y\right) \right) \right) [/tex]
axiom of foundation/regularity version 2:
[tex]V\left( \exists xA\left( x\right) \rightarrow \exists x\left(
V\left( A\left( x\right) \wedge \forall y\in x\left( !A\left( y\right)
\right) \right) =T\right) \right) =T[/tex]
11. axiom of choice (typo?):
[tex]\forall x\in a\exists A\left( x,y\right) \rightarrow \exists y\forall x\in
aA\left( x,y\left( x\right) \right) [/tex].
axiom of choice version 2:
[tex]V\left( \forall x\in a\exists A\left( x,y\right) \rightarrow
\exists y\forall x\in aA\left( x,y\left( x\right) \right) \right) =T[/tex]
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