In an excursus on "the structure of the Christian", Ratzinger addresses the tension between the gap, much stressed by Lessing, between vérité de fait and vérité de raison (or, contingent, historical truth and universal, rational truth). Addressing the tension is, however, only an oblique result of the larger contrast Ratzinger presents between Christian faith as a fundamentally passive, receptive stance toward God and the fundamentally active, combative nature of Marxism. Whereas Christianity rests upon a suffering-for, Marxism rests on a suffering-against. In the former, the Suffering Servant lays down his life for God's people; in the latter, the Persecuted Proletariat takes his place and lays down other (bourgeois) lives for the goal of a classless utopia. In the former case, God's people passively receive the Suffering Servant's vicarious life as a Gift; in the latter case, the proletariat aggressively take other lives in order to seize its destiny.
The problem Ratzinger sees with the Marxist's fundamental stance toward life is that it destroys man's most essential characteristic, namely, his radical and primary capacity to receive love, which he in turn reciprocates in freedom. Because a gift is by nature contingent, unnecessary, and particular, there is no choice but for man to appropriate it in accord with his own nature as a contingent, historical being. The upshot is that Ratzinger argues for the, so to speak, necessary contingency of divine revelation in history, in the proper mode of human existence. Revelation is necessarily subject to the weakness and uncertainty -- the contingency on 'that' side of the ditch -- of historical, empirical truth, since any other form of truth would either be a mere rational proposition or a corruption of man's dignity as a free, and free precisely because contingent, being. I would extend Ratzinger's argument a bit by saying, if the Gift were wrapped in pristine rationalist paper, it would then be the quasi-Marxist task of man to overthrow and 'cancel' -- quite in the sense of Hegel's Aufheben -- the 'decadent' régime of higher competing 'bourgeois' propositions, and thus, via action rather than reception, actively take in his own hand what is in fact essentially a Gift, a Gift not subject to seizing but only receiving in faith. The classless utopia of Marxism is analogous to the non-contingent, incorrigible utopia of pure rationalist certainty for which Lessing's critique, at least ostensibly, longs. If a perfect, mono-layered grasp of truth were the only goal of human knowledge, it would be the bitter duty of man to fight for the truth, in contrast to the Christian attitude of fighting on behalf of the truth -- yet only after one has received it in thanks and faith.
To return to Ratzinger's exposition: Christian revelation, in its anthropological dimensions, is rooted in a positivity, a phenomenological directness of either reception or rejection, that befits both the literally gratuitous nature of its object (life with God in Christ) and the contingent nature of man as a contingent, free being (un être de fait). In Ratzinger's own words:
…diese Verzerrung des Grundskandals christlichen Glaubens eine sehr tiefreichende Sache ist, der man weder mit Theorien noch mit Aktionen ohne weiteres beikommen kann. Ja, in gewissem Sinne wird hier erst die Eigenart des christlichen Skandals greifbar, nämlich das, was man den christlichen Positivismus, die unaufhebbare Positivität des Christlichen nennen könnte. Ich meine damit folgendes: Christlicher Glaube hat es gar nicht bloß, wie man zunächst bei der Rede vom Glauben vermuten möchte, mit dem Ewigen zu tun, das als das ganz andere völlig außerhalb der menschlichen Welt und der Zeit verbliebe; er hat es vielmehr mit dem Gott in der Geschichte zu tun, mit Gott als Menschen. Indem er so die Kluft von ewig und zeitlich, von sichtbar und unsichtbar zu überbrücken scheint, indem er uns [G]ott als einem Menschen begegnen läßt, dem Ewigen als dem Zeitlichen, als einem von uns, weiß er sich als Offenbarung. Sein Anspruch, Offenbarung zu sein, gründet ja darin, daß er gleichsam das Ewige hereingeholt hat in unsere Welt: »Was niemand je gesehen hat – der hat es uns ausgelegt, der an der Brust des Vaters ruht« (Joh 1,18) – er ist uns zur »Exegese« Gottes geworden, möchte man in Anlehnung an den griechischen Text beinahe sagen.
This distortion, or bias, of the fundamental scandal of Christian faith is a very deep-seated matter, and is overcome by neither theories, nor actions, nor anything else of the kind. Indeed, in a certain sense, only here is the uniqueness of Christian faith manifest, namely, in what one could call Christian positivism, the irrefragable positivity of the Christian. By that I mean the following: Christian faith has not only to do with the eternal (as many initially suspect in discussions of faith), with the totally 'other' remaining outside the human world and outside time. No, it has much more to do with God in history, with God as Human. In so far as He [Christ] appears to bridge the cleft between eternal and temporal, between visible and invisible; in so far as He allows us to encounter God as a man, the eternal as temporal, as one of us -- only thus is He truly known as revelation. His claim to be revelation is grounded in the fact that He has in one stroke incorporated the eternal into our world: "No one has ever seen God; the only Son, who is in the bosom of the Father, he has made him known." (John 1:18, RSV). He has become for the "exegesis" of God, if one may closely adapt from the Greek text.
(PDF WARNING: »Glauben in der Welt von heute« = Über das christliche Menschenbild, Das erste Kapitel aus Einführung in das Christentum. Vorlesungen über das Apostolische Glaubensbekenntis (München: Kösel, 1964) [my translation]
If the truth were just hanging "up there", "out there", it would be incumbent upon humans to strive with all their might to align themselves with a higher, unblinking truth. The radical gratuity of Christianity, however, cuts down at the knees such Marxist attempts, leaving man in awe as a recipient of grace he can not fight for but only accept.
Along similar lines I read with great interest C. Stephen Evans's analysis, in the eighth and ninth chapters of his The Historical Christ and the Jesus of Faith, of the covertly rationalist assumptions behind Lessing's supposedly empirical objection to revelation. The rationalist impetus of Lessing's critique transforms, wittingly or not, empirical difficulties as insurmountable a priori objections to any contingent expression or conception of divine truth. A theological rationalist (like Kant, Wittgenstein, or Hegel) assumes man should at some point just "see" or "get" religious truth, and so short of that numinous clarity, any empirical grounding for revelation ipso facto undercuts its claim to be truly transcendent revelation. The theological rationalist claims that while the path to the truth may not be easy, yet once it is attained it is no longer subject to empirical corroboration or refutation. In opposition to this halcyon vision of faith, Evans notes Kierkegaard's objections to theological rationalism by suggesting that the harder truth we must face is that man is actually not on such "good terms" with truth. If man were not a fallen, sinful creature, it would be safe to say we do just "get" truth. But since we are in fact fallen, freely cut off from God, God must "intrude" on our self-made noetic, spiritual horizons with some device that alters, jars, our whole perception of the world. And such an intrusion can only happen in a historical way, as an historical event. Hence, Evans is arguing that the constitution of man as a religious, albeit, flawed, being requires an historical revelation, including all the apparently messy problems of empirical uncertainty and contingency. Rationally, we might like to say, God would not do things this way, or, God would surely do things that way; but the big, historical, free, contingent fact is that or this is not how He did things: Christ is.
I believe Fr. Keefe's Covenantal Theology can shed tremendous light on these matters -- particularly with its emphasis on the radically free, and thus necessarily contingent intelligibility, of the Christ-event as a Gift -- but I haven't the time now to turn the spotlight any farther this way.