In January 2004 the Catholic Academy of Bavaria hosted a dialogue between what the German press quickly called the two "antipodes" of European intellectual life: the philosopher Jürgen Habermas, perhaps the most influential European thinker of recent decades, and Cardinal Joseph Ratzinger, then the Prefect of the Congregation for the Doctrine of the Faith (typically described as "the successor to the Inquisition"). The issue lurking in the background was the European Constitutional Treaty then being debated across the continent, and the ferocious argument over whether the treaty's preamble should acknowledge Christianity as one of the sources of 21st-­century Europe's commitments to civility, tolerance, human rights, the rule of law and democracy.

Habermas had been one of the vocal opponents of any such acknowledgment, taking the position (with Jacques Derrida) that the expanded European Union must be studiously "neutral between worldviews". Ratzinger, on the other hand, shared John Paul II's view that ignoring Christianity's contributions to European political culture was a self-­degrading act of historical amnesia: did Christianity really have nothing to do with tilling the cultural soil from which grew European man's convictions about his inalienable dignity? Moreover, Ratzinger intuited, there was future danger here. A Europe in which there was only "your truth" and "my truth", but nothing we both recognise as "the truth", would have a hard time maintaining a democratic form of government. The arts of political persuasion could work demo­crat­ic­ally only against a horizon of common moral reference points; in the absence of that horizon, someone would impose their power on someone else when "truths" came into conflict. Furthermore, Ratzinger believed, a Europe "neutral between worldviews" would be hard put to defend its commitments to the rule of law and the method of persuasion in politics if challengers with quite different and strongly held views of the just society - such as jihadist Islam - were to gain a purchase in European public life.