Owen Holden
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~(1/0 = 1/0)
Proof:
D1. 1/z =df (the x: 1=x*z & ~(z=0))
D2. G(the x: Fx) =df Ey(Ax(x=y <-> Fx) & Gy)
T1. ~(1/0 = 1/0)
Proof:
1. 1/z = 1/z <-> Ey(Ax(x=y <-> (1 = x*z & ~(z=0))) & y=y)
By, D1 and D2.
2. 1/0 = 1/0 <-> Ey(Ax(x=y <-> (1 = x*0 & ~(0=0))) & y=y)
By: 1, z=0.
3. 1/0 = 1/0 <-> EyAx(x=y <-> (1 = x*0 & ~(0=0)))
By: 2, y=y.
4. 1/0 = 1/0 <-> EyAx(x=y <-> contradiction)
By: 3, 0=0.
5. 1/0 = 1/0 <-> EyAx~(x=y)
By: 4, (x=y <-> contradiction) <-> ~(x=y).
6. 1/0 = 1/0 <-> ~AyEx(x=y)
By, 5, EyAx(~Rxy) <-> ~AyEx(Rxy)
7. 1/0 = 1/0 <-> contradiction
By: 6, AyEx(x=y).
8. ~(1/0 = 1/0)
By 7, (p <-> contradiction) <-> ~p.
Q.E.D.
Since, Exists(the x: Fx) <-> (the x: Fx)=(the x: Fx) is a theorem.
(See: Principia Mathematica *14.28 p 184)
T2. ~(Exists(1/0)), is also proven true.
If we can assert that Ax(x*0=0), then D1. is simplified.
D1a. 1/z =df (the x: 1=x*z), and the proof still works.
Any opinions?
Proof:
D1. 1/z =df (the x: 1=x*z & ~(z=0))
D2. G(the x: Fx) =df Ey(Ax(x=y <-> Fx) & Gy)
T1. ~(1/0 = 1/0)
Proof:
1. 1/z = 1/z <-> Ey(Ax(x=y <-> (1 = x*z & ~(z=0))) & y=y)
By, D1 and D2.
2. 1/0 = 1/0 <-> Ey(Ax(x=y <-> (1 = x*0 & ~(0=0))) & y=y)
By: 1, z=0.
3. 1/0 = 1/0 <-> EyAx(x=y <-> (1 = x*0 & ~(0=0)))
By: 2, y=y.
4. 1/0 = 1/0 <-> EyAx(x=y <-> contradiction)
By: 3, 0=0.
5. 1/0 = 1/0 <-> EyAx~(x=y)
By: 4, (x=y <-> contradiction) <-> ~(x=y).
6. 1/0 = 1/0 <-> ~AyEx(x=y)
By, 5, EyAx(~Rxy) <-> ~AyEx(Rxy)
7. 1/0 = 1/0 <-> contradiction
By: 6, AyEx(x=y).
8. ~(1/0 = 1/0)
By 7, (p <-> contradiction) <-> ~p.
Q.E.D.
Since, Exists(the x: Fx) <-> (the x: Fx)=(the x: Fx) is a theorem.
(See: Principia Mathematica *14.28 p 184)
T2. ~(Exists(1/0)), is also proven true.
If we can assert that Ax(x*0=0), then D1. is simplified.
D1a. 1/z =df (the x: 1=x*z), and the proof still works.
Any opinions?