Double Negation/Double Negation Introduction

Proof Rule
The rule of double negation introduction is a valid deduction sequent in propositional logic: If we can conclude $p$, then we may infer $\neg \neg p$.

It can be written:
 * $\displaystyle {p \over \neg \neg p} \neg \neg_i$

Variants
The following forms can be used as variants of this theorem:

Technical Note
When invoking Double Negation Introduction in a tableau proof, use the DoubleNegIntro template:



or:

where:
 * is the number of the line on the tableau proof where Double Negation Introduction is to be invoked
 * is the pool of assumptions (comma-separated list)
 * is the statement of logic that is to be displayed in the Formula column, without the  delimiters
 * is the line of the tableau proof upon which this line directly depends
 * is the (optional) comment that is to be displayed in the Notes column.