Single Idea 6561

[catalogued under 2. Reason / B. Laws of Thought / 3. Non-Contradiction]

Full Idea

It is impossible for the same thing at the same time both to be-in and not to be-in the same thing in the same respect.

Gist of Idea

A thing cannot be both in and not-in the same thing (at a given time)

Source

Aristotle (Metaphysics [c.324 BCE], 1005b19)

Book Reference

Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.88


A Reaction

Aristotle is really discussing non-contradiction here, but this formulation is very close to Leibniz's Law (that two identical things must have identical properties).