Conjunction elimination

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

In propositional logic, conjunction elimination (also called and elimination, ∧ elimination,[1] or simplification)[2][3][4] is a valid immediate inference, argument form and rule of inference which makes the inference that, if the conjunction A and B is true, then A is true, and B is true. The rule makes it possible to shorten longer proofs by deriving one of the conjuncts of a conjunction on a line by itself.

An example in English:

It's raining and it's pouring.
Therefore it's raining.

The rule consists of two separate sub-rules, which can be expressed in formal language as:


The two sub-rules together mean that, whenever an instance of "" appears on a line of a proof, either "" or "" can be placed on a subsequent line by itself. The above example in English is an application of the first sub-rule.

Formal notation[edit]

The conjunction elimination sub-rules may be written in sequent notation:


where is a metalogical symbol meaning that is a syntactic consequence of and is also a syntactic consequence of in logical system;

and expressed as truth-functional tautologies or theorems of propositional logic:


where and are propositions expressed in some formal system.


  1. ^ David A. Duffy (1991). Principles of Automated Theorem Proving. New York: Wiley. Sect., p.46
  2. ^ Copi and Cohen[citation needed]
  3. ^ Moore and Parker[citation needed]
  4. ^ Hurley[citation needed]