Law of noncontradiction

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.