"One important property of the absolute paradox for Kierkegaard is that it must be unique; the incarnation must somehow qualify as the absurd. However, there is nothing unique about a logical contradiction and no principled way to say that one is 'more contradictory' or 'absurd' than any other.
Furthermore, it is hard to see how a logical contradiction could serve as the 'boundary' or 'limit' of reason as the incarnation is supposed to do. To recognize a 'square circle' as a formal contradiction one must have a fairly clear grasp of the concepts of 'square' and 'circle'. In one sense at least, therefore, such a concept falls within the competence of reason; if it did not, reason could not properly classify it as a logical contradiction. The point of the incarnation, according to Kierkegaard, is that it is a concept that reason cannot understand.
Human reason is baffled both by human nature and by God. It is further baffled by the conjunction of the two concepts, but not because reason has a clear understanding of either what it means to be human or what it means to be God. The incarnation may appear or seem to human reason to be a logical contradiction, but it is not known to be such, and the believer does not think it is a formal contradiction."
C. Stephen Evans - Faith Beyond Reason: A Kierkegaardian Account