It's wrong because there can't be more than one thing. Yes, there can be multiple red M&M's, but no two are exactly the same. Therefore, the numeric identity theorum is not a bunch of crap. The teacher isn't right because SHE says so, she's right because what she says makes logical sense. If you had a twin, of course the twin would look like you...but does that mean the twin is you?

Cheers,
gilgalad