theorem

The law of non-contradiction is a rule of logic. It states that if something is true, then the opposite of it is false. For example, if an animal is a cat, the same animal cannot be not a cat. Or, stated in logic, if +p, then not -p, +p cannot be -p at the same time and in the same sense. The law was stated as a principle of mathematical logic by Russell and Whitehead in Principia Mathematica.[1]

Ravi Zacharias has said most eastern philosophies reject the law of noncontradiction.[2] The law of non-contradiction is found in ancient Indian logic as a rule in the Shrauta Sutras, the writing of Pāṇini,[3] and the Brahma Sutras attributed to Vyasa. It was later elaborated on by medieval commentators such as Madhvacharya.[4] The idea of noncontradiction is rejected in some strands of Buddhism.

## References

1. Alfred North Whitehead, Bertrand Russell (1910), Principia Mathematica, Cambridge, pp. 116–117
2. Zacharias, Ravi The Real Face of Atheism page 176
3. Frits Staal (1988), Universals: Studies in Indian Logic and Linguistics, Chicago, pp. 109–28 (cf. Bull, Malcolm (1999), Seeing Things Hidden, Verso, p. 53, ISBN 1-85984-263-1)
4. Dasgupta, Surendranath (1991), A History of Indian Philosophy, Motilal Banarsidass, p. 110, ISBN 81-208-0415-5