Sociological theory of evolution of religions, like theory of religious economy, adopts supply-side perspective on religious phenomena. It allows to redefine a problem of religious faith in terms of veracity, asking first “whom people believe” and “why him” before “who believes.” But taken in a perspective of system-theory, the veracity reveals its two-fold character. Religious organisation depends on its veracity in relation to its own believers but in different way its subsistence is conditioned by relations with other, non-religious actors in social environment, such as media, political or economic organisations. In this context, veracity becomes credibility. The paper argues that efforts made during Vatican II council to restore an external credibility had far-reaching consequences leading to erosion of internal veracity. Increase of transparency manifested in greater openness to mass-media, abandonment of claims to exclusivity in relations to the political sphere could cause a short-term crisis, but acceptance of the idea of ecumenism (which strongly silenced claims to be the only depositary of religious truth) and openness to scholarly inquiry on the very foundations of catholic dogmas, i.e. Bible and Tradition had much more important unintended effects. Questioning historical reliability of the New Testament (Jesuit Superior General Sosa Abascal noticed recently that “no one had a recorder to take down his words”) and faithfulness of transfer of the apostolic traditions resulted in gradual erosion of conviction in truthfulness of their own doctrine among catholic clergy or, at least, to uncertainty and doubt. It deprived them in their ability to enthuse their flock with faith and to lead their life in consistency with their own teachings.