If a door is sealed shut so that it really has no ability to open, is it still a door?
I had a big debate about this with my friends at supper one night. Some argued that it remained a door, still. Another idea was that it was a "post-door" as in it used to be a door. Naturally, that means it is a door no longer.
Despite posing the question in a neutral manner, I know that I took the side of it being no longer a door. The key to answering a philosophical question like this is having a perfect definition of everything. A door could be defined as something that opens to let people (or other things) through. This would mean that it is no longer a door. However, if the definition was modified only slightly, to something that was designed to open and let people through then it would still have a chance - unless you count the sealing as redesign with the intention of no longer letting people through.
Eventually you reach the conclusion that because a door is only a vague idea in the human conscious, the question cannot really be answered.