Before revision: History Ancient philosophy The earliest recorded use of the law appears to occur in Plato's dialogue Theaetetus (185a), wherein Socrates attempts to establish that what we call "sounds" and "colours" are two different classes of thing: It is used explicitly only once in Aristotle, in a proof in the Prior Analytics: Medieval philosophy Aristotle believed the law of non-contradiction to be the most fundamental law.
After revision: History Ancient philosophy The earliest recorded use of the law appears in Plato's dialogue Theaetetus (185a), wherein Socrates attempts to establish that what we call "sounds" and "colours" are two different classes of thing: It is used explicitly only once in Aristotle, in a proof in the Prior Analytics: Medieval philosophy Aristotle believed the law of non-contradiction to be the most fundamental law.