Occurs when a generalization is made about a seemingly sensible rule, but this sensible rule doesn't work well in all situations.
Example: Stealing is bad.
(This is mostly true; however, what about stealing bread to feed your starving children? Are there occasional exceptions to some generally agreed upon rules?)
Example: One should return borrowed items when the person who loaned them wants them back.
(Mostly true... unless your neighbor--who has always been nice to you but has recently been suffering from psychotic episodes--wants the rifle he loaned you for hunting season back moments after threatening to kill a different neighbor...)
Example: Never talk to strangers.
(A good policy... unless, of course, you've fallen off of a cliff, broken your leg, and a stranger happens to be hiking past.)