A law in (2-valued) logic which states there is no third alternative to truth or falsehood.
In other words, for any statement 
, either 
or not-
must be true and the other must be false. This law no longer
holds in three-valued logic or fuzzy
logic.
Law of the Excluded Middle
See also
Bivalent, Fuzzy Logic, Three-Valued LogicExplore with Wolfram|Alpha
References
Erickson, G. W. and Fossa, J. A. Dictionary of Paradox. Lanham, MD: University Press of America, pp. 64-65, 1998.Referenced on Wolfram|Alpha
Law of the Excluded MiddleCite this as:
Weisstein, Eric W. "Law of the Excluded Middle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/LawoftheExcludedMiddle.html