Single Idea 12130

[catalogued under 9. Objects / F. Identity among Objects / 7. Indiscernible Objects]

Full Idea

Suppose that a and b have all of their properties in common. a certainly has the property of-being-identical-with-a. So, by supposition, does b. Then a = b.

Gist of Idea

a and b share all properties; so they share being-identical-with-a; so a = b

Source

Baruch Brody (Identity and Essence [1980], 1.2)

Book Reference

Brody,Baruch: 'Identity and Essence' [Princeton 1980], p.9


A Reaction

Brody defends this argument, and seems to think that it proves the identity of indiscernibles. As far as I can see it totally begs the question, since we can only assume that both have the property of being-identical-with-a if we have assumed a = b.