Law of Non-Contradiction
The Law of Non-Contradiction can be formulated as follows: Two truths cannot contradict one another.
On the other hand, for any pair of contradictory premises, one must be true and the other false. The Law of Non-Contradiction prevents both premises being true, while the Law of Excluded Middle points out that a pair of contradictory premises exhausts all possibilities. Another way of putting it is: a proposition must be either true or false—not both true and false, nor in some limbo state in between truth and falsity. This can be useful in listing all possible alternatives and refuting all of them but the correct one.
- Galileo Galilei (1615, 1998). Letter to the Grand Duchess Christina of Tuscany. Internet History Sourcebooks Project, Paul Halsall, [The Jesuit] Fordham University [of New York]. Retrieved on June 10, 2013.
- Jonathan D. Sarfati. Loving God with all your mind: logic and creation. CMI. Retrieved on June 10, 2013.