In his recent LRB article on Wikileaks, "Good Manners in the Age of WikiLeaks" (recommended), Slavoj Žižek (2011) answers:
In Baisers volés, Delphine Seyrig explains to her young lover the difference between politeness and tact: ‘Imagine you inadvertently enter a bathroom where a woman is standing naked under the shower. Politeness requires that you quickly close the door and say, “Pardon, Madame!”, whereas tact would be to quickly close the door and say: “Pardon, Monsieur!”’ It is only in the second case, by pretending not to have seen enough even to make out the sex of the person under the shower, that one displays true tact.
