Law of identity

The Law of identity in logic, often incorrectly attributed to Aristotle, states that A = A.

By the 17th century, reference to the law of identity was common amongst philosophers, but no reference to it exists during or before the time of St. Thomas Aquinas in the 13th century. It is probable that the law of identity was posited from Aristotle's teachings sometime between 13th and 17th centuries, during which time it became commonly and mistakenly accepted as being something Aristotle himself authoritatively stated.