Proving \neg x \vee x in Hilbert System: A Logical Dilemma

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Homework Help Overview

The discussion revolves around proving the logical expression \neg x \vee x using a Hilbert system. Participants express uncertainty regarding the axioms applicable in this context and the nature of the Hilbert system itself.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the logical axioms relevant to the proof and question whether a standard set exists. There is an exploration of how to apply the axioms to prove the expression, with some expressing confusion about the implications of the axioms.

Discussion Status

Some participants have provided insights into the nature of the expression being always true, while others emphasize the need for a formal proof within the Hilbert system. There is a request for clarification on the specific axioms that can be utilized, indicating a productive direction in the discussion.

Contextual Notes

Participants note a lack of familiarity with the Hilbert system compared to Hilbert space, which may affect their understanding of the proof process. There is also mention of varying sets of axioms that could be used in the proof.

hamsterman
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Homework Statement


Prove \neg x \vee x using Hilbert system.

Homework Equations


The logical axioms. I'm not sure if I should state them, or whether there is a standard set. It seems to me that different sets are used. Anyway, the ones with disjunction in them are:
a \rightarrow a \vee b
(a \rightarrow c) \rightarrow ((b \rightarrow c) \rightarrow (a \vee b \rightarrow c))

The Attempt at a Solution


If I wanted to use the first axiom, I'd have to prove x, which can be false. If I used the second axiom, I'd get what I wanted on the wrong side of the arrow. I don't think there is a way to reverse an arrow, except for (x \rightarrow y) \rightarrow (\neg y \rightarrow \neg x), but then I'd have no way to get rid of the negation. I'm lost. I'd appreciate help.
 
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hamsterman said:

Homework Statement


Prove \neg x \vee x using Hilbert system.

Homework Equations


The logical axioms. I'm not sure if I should state them, or whether there is a standard set. It seems to me that different sets are used. Anyway, the ones with disjunction in them are:
a \rightarrow a \vee b
(a \rightarrow c) \rightarrow ((b \rightarrow c) \rightarrow (a \vee b \rightarrow c))

The Attempt at a Solution


If I wanted to use the first axiom, I'd have to prove x, which can be false. If I used the second axiom, I'd get what I wanted on the wrong side of the arrow. I don't think there is a way to reverse an arrow, except for (x \rightarrow y) \rightarrow (\neg y \rightarrow \neg x), but then I'd have no way to get rid of the negation. I'm lost. I'd appreciate help.

This seems like a lot of work to evaluate a very simple logical expression that is always true.
If x is true, then ~x is false, in which case ~x V x is true.
If x is false, then ~x is true, in which case ~x V x is again true.

How this fits into the Hilbert system, I have no idea, since that's a new one on me. I'm familar with Hilbert space, but not the Hilbert system.
 
Mark44 said:
This seems like a lot of work to evaluate a very simple logical expression that is always true.
If x is true, then ~x is false, in which case ~x V x is true.
If x is false, then ~x is true, in which case ~x V x is again true.

How this fits into the Hilbert system, I have no idea, since that's a new one on me. I'm familar with Hilbert space, but not the Hilbert system.

There there is something called the Hilbert system, but it's actually called Hilbert–Ackermann system.
 
I know it is true. That fact does not interest me. The proof using Hilbert system does.
 
Can you list all of the axioms you are allowed to use? Like you said sometimes different sets are used, it'd be easier if we knew what ones you could use.
 

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