1Co 11:19 For there must be also heresies among you, that they which are approved may be made manifest among you.

Now I know.

Is this like the saying, "You wouldn't know how good good was if there wan't bad?"

I can't wait for heaven when there is no such thing as yang....only yin (or maybe the other way around, I can't remember which one is which, but you know what I mean).