How to prove a set of propositional connectives is NOT adequate?

  • Context: Undergrad 
  • Thread starter Thread starter philoss
  • Start date Start date
  • Tags Tags
    Set
Click For Summary

Discussion Overview

The discussion revolves around the question of how to prove that a set of propositional connectives is not adequate, specifically focusing on the set {and, or}. Participants explore the implications of lacking certain connectives, such as "NOT," in generating all necessary logical relationships.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Homework-related

Main Points Raised

  • One participant seeks clarification on how to demonstrate the inadequacy of a set of connectives, specifically asking for methods to prove that {and, or} cannot generate all connectives.
  • Another participant provides a link to a resource that may assist in understanding the concept of adequacy in propositional logic.
  • A participant notes that the absence of the "NOT" operator in the set {and, or} is a key reason it is not adequate, as it is necessary for forming implications.
  • There is a mention of a distinction between propositional logic and philosophical logic, suggesting that this difference may affect how such questions are approached.

Areas of Agreement / Disagreement

Participants appear to agree on the necessity of the "NOT" operator for completeness, but there is no consensus on the methods for proving inadequacy or the implications of the distinction between propositional and philosophical logic.

Contextual Notes

Limitations include the lack of detailed proofs or specific methodologies for demonstrating inadequacy, as well as the dependence on definitions of adequacy and completeness in propositional logic.

philoss
Messages
1
Reaction score
0
I know how to prove if a set is adequate (all the main conncectives can be made from the set), but how would you prove that it is impossible to make all the connectives using this set?
For instance how would you prove if a set of connectives {and, or} is NOT adequate?

This is a question I thought of for preperation for a exam.

Any answer is appreciated.

Thanks
 
Physics news on Phys.org
Note that on the site I posted, K = "NOT 2nd" and M = "NOT 1st."

Also from http://en.wikipedia.org/wiki/Functional_completeness#Informal I surmise that {and, or} is not adequate because the "NOT" operator, which is excluded from the set, is necessary for generating the "--->" (if/then; implies) relationship.
 
Last edited:
Note: moved this thread from Philosophy. This will likely be a better place to get help with this type of question.
 
I agree; I guess there is a difference between propositional logic and "philosophical" logic, and sometimes it gets ignored.
 

Similar threads

  • · Replies 18 ·
Replies
18
Views
4K
  • · Replies 11 ·
Replies
11
Views
1K
  • · Replies 3 ·
Replies
3
Views
454
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
14
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K