From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
In discussing these currents of thought, it has not been my intention to present a complete picture of the present state of philosophy, which would, in any case, be difficult to reduce to a unified vision. And I certainly wish to stress that our heritage of knowledge and wisdom has indeed been enriched in different fields. We need only cite logic, the philosophy of language, epistemology, the philosophy of nature, anthropology, the more penetrating analysis of the affective dimensions of knowledge and the existential approach to the analysis of freedom. Since the last century, however, the affirmation of the principle of immanence, central to the rationalist argument, has provoked a radical requestioning of claims once thought indisputable. In response, currents of irrationalism arose, even as the baselessness of the demand that reason be absolutely self-grounded was being critically demonstrated.
Our age has been termed by some thinkers the age of “postmodernity”. Often used in very different contexts, the term designates the emergence of a complex of new factors which, widespread and powerful as they are, have shown themselves able to produce important and lasting changes. The term was first used with reference to aesthetic, social and technological phenomena. It was then transposed into the philosophical field, but has remained somewhat ambiguous, both because judgement on what is called “postmodern” is sometimes positive and sometimes negative, and because there is as yet no consensus on the delicate question of the demarcation of the different historical periods. One thing however is certain: the currents of thought which claim to be postmodern merit appropriate attention. According to some of them, the time of certainties is irrevocably past, and the human being must now learn to live in a horizon of total absence of meaning, where everything is provisional and ephemeral. In their destructive critique of every certitude, several authors have failed to make crucial distinctions and have called into question the certitudes of faith.
This nihilism has been justified in a sense by the terrible experience of evil which has marked our age. Such a dramatic experience has ensured the collapse of rationalist optimism, which viewed history as the triumphant progress of reason, the source of all happiness and freedom; and now, at the end of this century, one of our greatest threats is the temptation to despair.
Even so, it remains true that a certain positivist cast of mind continues to nurture the illusion that, thanks to scientific and technical progress, man and woman may live as a demiurge, single-handedly and completely taking charge of their destiny.
— Fides et Ratio 91