In Kierkegaard and the Patristic and Medieval Traditions (Ashgate), Pierre Bühler writes a chapter entitled, “Tertullian: The Teacher of the credo quia absurdum.” Here are some excerpts:
The book De carne Christi is a defense of the Incarnation, against Gnostic and Marcionist docetism. Working with passages from the apostle Paul, especially his “word of the cross” in 1 Corinthians 18-25, Tertullian emphasizes, contrary to Marcion’s Gnostic “wisdom,” the necessary foolishness of Christ’s incarnation, in his birth, in his life, and above all in his death and resurrection. And so Tertullian, with rhetorical dexterity, can write: “God’s Son has been crucified? I am not ashamed because one has to be ashamed. And God’s Son is dead? It is credible because it is inept. And the buried rose from the dead? It is certain because it is impossible.”*
* * *
Against the philosophical systems that do not worry about faith, leaving it behind themselves, Kierkegaard emphasizes the idea that faith is the main goal of life, so that we can never can go further than faith. This is what he tries to show with the character of Abraham in Fear and Trembling: even though Tertullian’s formula does not appear in this book, it informs implicitly the whole purpose. Abraham’s faith is “by virtue of the absurd” and therefore it places Abraham apart, tears him out of the generally human perspective, puts him in an absolute relationship to the absolute. Only from there will it be possible for him to live his life, coming back from the extreme trial and rediscovering everything in a new light. Throughout his whole work, Kierkegaard constantly stressed this connection between faith and the absurd. Therefore, even if Tertullian’s formula does not appear everywhere in Kierkegaard’s writings, it refers to a central aspect of his understanding of Christianity.
If the absurd is so important, what does it mean for the relationship between faith and reason? Shall faith ask for a sacrificium intellectus? Does the credo quia absurdum lead to an anti-rationalism?
The relationship between absurdity, faith and understanding is much more dynamic. The absurd does not constrain the believer to give up his understanding. On the contrary, as Kierekgaard explains at the end of his Concluding Unscientific Postscript in an interesting passage:
Consequently the believing Christian both has and uses his understanding, respects the universally human, does not explain someone’s not becoming a Christian as a lack of understanding, but believes Christianity against the understanding and here uses the understanding–in order to see to it that he believes against the understanding. Therefore he cannot believe nonsense against the understanding, which one might fear, because the understanding will penetratingly perceive that it is nonsense and hinder him in believing it, but he uses the understanding so much that through it he becomes aware of the incomprehensible, and now, believing, he relates himself to it against the understanding.
Could this text be an answer to the objection of anti-rationalism, which Tertullian is often reproached of? If we answer with yes, we recognize Kierkegaard as a worthy heir of Tertullian, or Tertullian as a venerable ancestor of Kierkegaard. But then Kierkegaard would respectfully ask: “what similarity is there between me and Tertullian?”
* My (literal) translation. Crucifixus est Dei Filius, non pudet, quia pudendum est; et mortuus est Dei Filius, prorsus credibile est, quia ineptum est; et sepultus resurrexit, certum est, quia impossibile. “The Son of God was crucified: I am not ashamed – because it is shameful. The Son of God died: it is immediately credible – because it is silly. He was buried, and rose again: it is certain because it is impossible.”