When Pope Benedict XVI lifted the excommunication of four bishops from the traditionalist Society of St. Pius X, including Holocaust denier Richard Williamson, on January 21, 2009, it represented another act in the contentious struggle of the Catholic Church with an enlightened modernity. Since the 19th century, the Catholic Church has responded to the challenges of modernity by reaffirming papal primacy and defending traditional teachings. Around the turn of the 20th century, theologians and thinkers such as Alfred Loisy, George Tyrrell, Romolo Murri, and Hermann Schell sought to reconcile dogma with scientific knowledge and societal developments, and to formulate theology based on modern assumptions. Pope Pius X and the Roman Curia condemned these efforts.