Can I Un that?

As I was getting ready to go to work today I had an epiphany, well maybe short of an epiphany, but definitely a realization. I can't for the life of me think of a positive use of the prefix Un. Is there one? I will have to look and see. But right off hand I can not think of one. I know that many, if not all words that the prefix Un can be attached to end up having a negative connotation.

Unresponsive
Undesirable
Unwanted
Unneeded
Unused
Unwilling
Unwelcome
Uneducated
Undefined
Unnecessary

All words that come to mind when thinking of the prefix Un. But can we simply attach the Un to any word to infer the opposite meaning of that word?

Unevil?
Unvile?
Unhated?
Unrejected?
Undespised?
Undejected?
And on and on and on.....

I am sure there is a regulation within the mechanics of language that dictates what can and cannot be Un'ed. I do not know it. So if you do let me know, okay. Anyway, just thought I would pass this along as it's one of those odd things that popped in my head and needed to be written down before it escaped.

Hopefully my thoughts on the subject are fully Understandable. Which of course leads me to ask what is derstandable?

Today's Rant:Complete