Single Idea 6049

[catalogued under 9. Objects / F. Identity among Objects / 8. Leibniz's Law]

Full Idea

Leibniz's Law says 'x = y iff for all P, Px iff Py'.

Clarification

'Iff' means if and only if; Px means x has the property P

Gist of Idea

Leibniz's Law says 'x = y iff for all P, Px iff Py'

Source

Colin McGinn (Logical Properties [2000], Ch.1)

Book Reference

McGinn,Colin: 'Logical Properties' [OUP 2003], p.7


A Reaction

That is, two things are the same if when we say that one thing (x) has a property (P), then we are saying that the other thing (y) also has the property. A usefully concise statement of the Law.