## 7.4 Negation and contradiction

### 7.4.1 `Absurd` term``

This tactic applies to any goal. The argument term is any proposition `P` of type `Prop`. This tactic applies `False` elimination, that is it deduces the current goal from `False`, and generates as subgoals `~``P` and `P`. It is very useful in proofs by cases, where some cases are impossible. In most cases, `P` or ~`P` is one of the hypotheses of the local context.

### 7.4.2 `Contradiction`

This tactic applies to any goal. The `Contradiction` tactic attempts to find in the current context (after all `Intros`) one which is equivalent to `False`. It permits to prune irrelevant cases. This tactic is a macro for the tactics sequence `Intros; ElimType False; Assumption`.
Error messages:

1. `No such assumption`