The year 2016 has been consecrated as the year of post-truth. According to the Oxford dictionary, which has made it its word of the year, this term would refer to "circumstances in which objective facts have less influence in forming public opinion than the appeal to emotion and personal beliefs". This book goes back to the source of this state of affairs and identifies it in the concept of "bullshit" theorized by the philosopher Harry Frankfurt in 1986. What he defined as "indifference to truth" as distinct from lying is indeed a remarkably effective conceptual tool for grasping how opinion claims to prevail over truth and for understanding the success of intellectual deception and "conspiracy theories". The post-truth era is indeed the era of the global bullshit, and only an in-depth understanding of this phenomenon will enable us to engage in the struggle that is about to begin.