Abstract
The ideology of post-truth is increasingly receiving a central role in public communication. This idea does not consist in observing that politicians often lie, but in the statement that lying is not wrong, because it is communicative effectiveness what matters. Success, first measured through the “like” of social networks and then with votes in the polls, is what matters and no one should stigmatize whoever lies to get it . Libraries, public and special, as they have become, can not survive if this ideology prevails. Their role implies that it is possible to discriminate valid documents - documents based based on the principles of widely-understood scientific research - from documents that are not based on scientific research. Librarians are useful if they can help their users to chose “right” books, article, papers for their needs, but to do this they need an axiological criterion based on epistemological criteria. Without these criteria libraries as defined entities managed using professional criteria can not exist. As an example of what means post-truth ideology, this paper discuss the case of statistical information.