law of double negation

The **law of double negation** is the statement that the double negation of a proposition implies that proposition

$\not \not A \Rightarrow A
\,.$

In classical logic, this is simply true. In constructive logic, it is equivalent to the law of excluded middle (because $\not \not (P \vee \not P)$ is a constructive theorem), and is not assertable in general.

Last revised on March 30, 2017 at 03:49:51. See the history of this page for a list of all contributions to it.