In his Natural Right and History, Strauss observes that “Kant has interpreted the teachings of Rousseau’s Second Discourse as a vindication of Providence. Accordingly, the idea of history, precisely like modern political economy, could appear to have emerged through a modification of the traditional belief in Providence. That modification is usually described as “secularization.” (Page 317).
Here’s Strauss’s explanation of the role that the idea of secularization has played in modern thinking (Page 317):
"Secularization" is the "temporalization" of the spiritual or of the eternal. It is the attempt to integrate the eternal into a temporal context. It therefore presupposes that the eternal is no longer understood as eternal. "Secularization," in other words, presupposes a radical change of thought, a transition of thought from one plane to an entirely different plane. This radical change appears in its undisguised form in the emergence of modern philosophy or science; it is not primarily a change within theology. What presents itself as the "secularization" of theological concepts will have to be understood, in the last analysis, as an adaptation of traditional theology to the intellectual climate produced by modern philosophy or science both natural and political. The "secularization'' of the understanding of Providence culminates in the view that the ways of God are scrutable to sufficiently enlightened men.The theological tradition used to hold that the designs of God in history are inscrutable to man, but the modern philosophers like Burke and Rousseau thought that they could divine God's Providence. But if the historical process is itself rational then the ground of morality — the distinction between good and evil — loses its meaning. And this kind of thinking leads to the lowering of the goals of human action. Strauss writes:
The theological tradition recognized the mysterious character of Providence especially by the fact that God uses or permits evil for his good ends. It asserted, therefore, that man cannot take his bearings by God's providence but only by God's law, which simply forbids man to do evil. In proportion as the providential order came to be regarded as intelligible to man, and therefore evil came to be regarded as evidently necessary or useful, the prohibition against doing evil lost its evidence. Hence various ways of action which were previously condemned as evil could now be regarded as good. The goals of human action were lowered. But it is precisely a lowering of these goals which modern political philosophy consciously intended from its very beginning.