John Paul II formerly taught philosophy, and one might say that in is Fides and Ratio he addresses his peers… whatever their opinion as regards the faith. The Pope shows the specificity of the «knowledge of faith» vis-à-vis all other knowledges: limited as it be (yet precise), it is primarily a personal knowledge (the science of Christ) and it endowed with redeeming power. What reaction will the encyclical elecit in philosophical spheres? While admitting that modern and contemporary philosophy has merits of its own, the Pope does not spare his (rather blunt) criticism, especially of post-modern versions. The present article explores the possibility of a dialogue.