Ever since we bought a
hatchback car two years ago, I have found the method of protecting the contents of the
trunk very amusing. Because there is no real trunk, the contents stored in the back are clearly
visible through the
rear window. In order to provide some measure of
security, there is a
plastic/
vinyl tarp-like thing that has been installed that can be pulled down over whatever is in the back, shielding it from view. This is done so that whatever
valuables are there cannot be seen from the
outside.
Now this on the surface seems to be a pretty good idea. I wouldn't want my stereo attracting the eye of anybody walking by the car. The problem that I find with it, however, is that the system itself seems to be self-defeating. It seems to me that the presence of the tarp would cause a burglar to break into the car almost as much as seeing the content themselves. The reason why is this: the tarp exists to protect the contents of the trunk from being seen. People only use the tarp when there is something in the back that they don't want anybody to see (if the trunk were empty or contained say a pile of sticks, we wouldn't bother covering it) and they don't want it to be seen because they don't want it stolen. Therefore if the tarp is pulled over, there is something in the trunk that is worthy of being stolen. In effect, by covering the back with the tarp, the owner is in fact telling me that there is something to steal.
I have come to call this a Persistent Knowledge Situation because if there is something valuable in the back, there is nothing you can do to prevent me from learning of that fact. If the item is left visible, then I can tell that the item is valuable because I can see for myself. If it is concealed however, I still know that there is something valuable by the mere fact that it is being concealed. Either way, I am aware of its presence.
Now of course, this is not completely true, nor is it necessarily always the case (otherwise I assume there would be other protection). There are of course advantages to covering up whatever is in the trunk. First of all, I don't technically know that there is anything in the back. The trunk could be empty and still be concealed, and that is a risk I'd have to take. On the other hand, I don't think that too many people conceal their trunks if they have nothing to hide. The second, and most important reason why it is good to cover something up is because even if it does alert me to the fact that there is something in the trunk that the owner doesn't want stolen, it doesn't necessarily mean that whatever's there is valuable or worth the effort of breaking in. I don't know what is there - it could be a thousand-dollar stereo or it could be a box of used books. This makes it a big risk for me, and I imagine that it is this risk that makes the whole thing work. People are unwilling to go through the effort of breaking into a car if they don't know what the payoff will be.
I still find the whole situation very fascinating because in its generalized form, the method of preventing the knowledge in fact provides the same information. I saw another example of this recently when I saw the X-Men film. Magneto is taking over the Statue of Liberty and the X-Men set off to stop him. In order to shield their approach, the character Storm causes a dense fog to roll in, covering their plane. Magneto is not fooled by this however - he notices it and realizes that it is in fact the creation of the X-Men, alerting him to their presence. Storm's attempt to conceal their approach has instead alerted him to it!
The reason I think that both of these methods (trunk tarp and Storm's fog) are fallible is based on the probability of these things occurring normally. For the most part, a hatchback trunk will not be covered if there is nothing there, and a fog rolling in right as Magneto begins his attack is rather unlikely. Therefore, their presence is significant. The only way that I can see for the hatchback setup to truly work is if everybody covered up their trunk all the time. Then, the presence of the tarp would not be anything of the ordinary and would not implicitly signify anything.