---
tags:
  - Logic
  - propositional-logic
  - derivation-rules
---

![negate-elim 1.png](../img/negate-elim%201.png) 
Like the [introduction](Negation%20Elimination.md) rule for negation, the elimination rule also works by deriving a contradiction. It is basically *Negation Introduction* in reverse. Instead of starting the subproof with a true proposition from which you derive a contradiction, you start with the negation of a proposition, derive a contradiction and then assert the positive of the negated proposition you started out with.
