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GeneralRe: "Don't be evil" Pin
Roger Wright18-Apr-15 20:41
professionalRoger Wright18-Apr-15 20:41 
GeneralRe: "Don't be evil" Pin
Kenneth Haugland18-Apr-15 23:43
mvaKenneth Haugland18-Apr-15 23:43 
GeneralRe: "Don't be evil" Pin
A. A. J. Rodriguez20-Apr-15 3:50
A. A. J. Rodriguez20-Apr-15 3:50 
GeneralRe: "Don't be evil" Pin
Kenneth Haugland20-Apr-15 4:20
mvaKenneth Haugland20-Apr-15 4:20 
GeneralRe: "Don't be evil" Pin
A. A. J. Rodriguez20-Apr-15 17:44
A. A. J. Rodriguez20-Apr-15 17:44 
GeneralRe: "Don't be evil" Pin
Kenneth Haugland20-Apr-15 22:56
mvaKenneth Haugland20-Apr-15 22:56 
GeneralRe: "Don't be evil" Pin
jibalt20-Apr-15 16:26
jibalt20-Apr-15 16:26 
GeneralRe: "Don't be evil" Pin
A. A. J. Rodriguez20-Apr-15 17:36
A. A. J. Rodriguez20-Apr-15 17:36 
jibalt wrote:
Gödel's second incompleteness theorem states that a consistent system cannot prove its own consistency. And of course inconsistent systems can prove anything, true or false, including their consistency.


It's better said that if a system S includes a statement about its own consistency, then by definition S is inconsistent. To demonstrate its consistency, you have to include statements that are outside of S.


jibalt wrote:
This is an odd and confusing way to state these, as it isn't clear that they are universally qualified.


Granted, that's the way I learned it, but we could nitpick all day, since it should say:

Consistency: For all X \in S, ...

because there are statements outside of S that can "declare" the completeness of S. Of course, that would create a new system S_0, which has its own "Godel sentence". And so on.

jibalt wrote:
If G could be proved, that would be a contradiction, making the system inconsistent. And since it cannot be proved, it's true.


It's not that "since it cannot be proved, it's true"; every false statement in S could be considered true by that phrase, which would break consistency.

My understanding of Godel's ITs (once again, as someone who's still grasping wisps of understanding about it): If a system has to discard either consistency or completeness, consistency is more important, so completeness goes out the window. G has to be true and unproven, violating completeness, since proving G would violate consistency, which defeats the purpose of having the system in the first place.

(Apologies for leaving out the o with the dieresis atop; Godel deserves to have his name written correctly, but I'm at a loss on how to type it with my current keyboard settings.)
GeneralRe: "Don't be evil" Pin
jibalt28-Apr-15 2:06
jibalt28-Apr-15 2:06 
GeneralRe: "Don't be evil" Pin
A. A. J. Rodriguez28-Apr-15 6:59
A. A. J. Rodriguez28-Apr-15 6:59 
GeneralRe: "Don't be evil" Pin
Daniel Pfeffer18-Apr-15 23:51
professionalDaniel Pfeffer18-Apr-15 23:51 
GeneralRe: "Don't be evil" Pin
908236520-Apr-15 1:45
908236520-Apr-15 1:45 
GeneralRe: "Don't be evil" Pin
Ron Anders18-Apr-15 14:43
Ron Anders18-Apr-15 14:43 
GeneralRe: "Don't be evil" Pin
Sascha Lefèvre18-Apr-15 14:56
professionalSascha Lefèvre18-Apr-15 14:56 
GeneralRe: "Don't be evil" Pin
BupeChombaDerrick18-Apr-15 15:02
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GeneralRe: "Don't be evil" Pin
DaveX8618-Apr-15 16:28
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GeneralRe: "Don't be evil" Pin
Mark_Wallace18-Apr-15 22:10
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GeneralRe: "Don't be evil" Pin
OriginalGriff19-Apr-15 0:13
mveOriginalGriff19-Apr-15 0:13 
GeneralRe: "Don't be evil" Pin
Mark_Wallace19-Apr-15 1:10
Mark_Wallace19-Apr-15 1:10 
GeneralRe: "Don't be evil" Pin
Mark_Wallace18-Apr-15 20:26
Mark_Wallace18-Apr-15 20:26 
GeneralRe: "Don't be evil" Pin
Sascha Lefèvre19-Apr-15 1:42
professionalSascha Lefèvre19-Apr-15 1:42 
GeneralRe: "Don't be evil" Pin
Member 1130387220-Apr-15 3:09
Member 1130387220-Apr-15 3:09 
GeneralRe: "Don't be evil" Pin
Steve Wellens18-Apr-15 17:21
Steve Wellens18-Apr-15 17:21 
GeneralRe: "Don't be evil" Pin
BupeChombaDerrick19-Apr-15 9:12
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GeneralRe: "Don't be evil" Pin
Mark_Wallace18-Apr-15 20:30
Mark_Wallace18-Apr-15 20:30 

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