In this prison, the cells were arranged in a ring around a central tower that contained a guard. The guard could see out, but the prisoners could not see in. What kept people in check under this system was not actually being watched, but the threat of being watched. For all any of the prisoners knew, the guard could be looking at them at any given moment, so the idea was that they would always behave as if the guard were watching them, whether or not he actually was watching. The system was effective because it provoked anxiety in the prisoners, and controlled by imposing the values of the jailor on the prisoner. This system is often used as a metaphor for today's methods of surveillance. Many of us actually censor ourselves (self-censorship) because we are afraid of what the government might believe about us if they are keeping track of our online search history. As we have discovered in the past few years, the NSA actually collects a great deal of information about our online activities. This may potentially cause fear, and reservation about researching certain ideas (e.g. socialism, Islam, or gun rights). Ideas that are protected by the very constitution itself (1st amendment). Without the ability to stay informed about ideas that are not mainstream, we undermine the pluralistic nature of a true democracy. This consideration for privacy is one of the reasons libraries do not provide histories of patron checkouts to the government, or even retain them after the items have been returned.