Modern reason inherits a legacy of questions from medieval Christian thought which it is not really suited to answer, and overextends itself trying to answer them anyway. Thus it is that modern thought tries to extend the idea of progress into a philosophy of history to answer the inherited medieval questions about the shape of history (the question to which eschatology was the medieval answer).
53-54: "Augustine's explanation of the bad in the world as the result of human wickedness, as a species-wide quantity, made it necessary for any subsequent notion of progress that would undertake to diminish the bad in the world also to establish man's ability to lessen his culpability by his own efforts. The idea of progress, as was to become evident much later on, requires a reversal of the causal relation between moral and physical evils; it is founded on the assumption that in a better world it would be easier to be a better person."
Marquard - Modern philosophy of history takes on the function of theodicy. Here, Blumenberg's functional analysis of history actually provides a final foothold for the secularization thesis.Blumenberg responds that philosophy of history as the story of progress cannot actually perform the function of theodicy. Theodicy requires a subject with perfect freedom to absolve God for the responsibility for bad things, but freedom is seen as the end of philosophy of history, not its presupposition. In any case, the functional analysis of philosophy of history seeks only to explain it as an ultimately unavoidable response to the provocation of medieval thought, it does not seek to justify it.