nLab law of double negation




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

¬¬AA. \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 ¬¬(P¬P)\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.