Law of the excluded middle

The law of the excluded middle is a simple rule of logic. It states that for any proposition,a proposition is, very roughly, a statement which is claimed to be true there is no middle ground. Every proposition is either true or false.
Example
For example, "Ginger is a cat" says the fact that Ginger is a cat. If it is true, then its opposite cannot also be true. If Ginger is a cat, then Ginger is not something else.Bennett, Deborah Logic Made Easy page 30
Mathematics
In mathematics, the law of the excluded middle is a presupposition behind the proof by contradiction. Because of that, those who reject the validity of the law of the excluded middle (for example, the intuitionists) must also reject the validity of proof by contradiction as well.

 Related pages 

 Law of noncontradiction

 Notes 

Category:Logic