law of contradiction

The law of contradiction, also known as the principle of contradiction, is a fundamental principle in logic. It states that a thing cannot simultaneously exist and not exist in the same respect. For example, a table cannot be both a table and not a table at the same time.1

In logic, contradictories are statements that are opposed in both quantity and quality, meaning one is universal and the other is particular, with one being an affirmation and the other a denial. These statements cannot both be true and cannot both be false; if one is true, the other must be false.2