Christianity is the emancipation of the human race from the bondage of that inimical spirit who denies God, and, as far as in him lies, leads all created intelligences astray. Hence the Scripture styles him, "the prince of this world;" and so he was in fact, but in ancient history only, when among all the nations of the earth, and amid the pomp of martial glory, and the splendour of Pagan life, he had established the throne of his domination. Since this divine era in the history of man, since the commencement of his emancipation in modern times, this spirit can no longer be called the prince of this world, but the spirit of time [Zeitgeist], the spirit opposed to divine influence, and to the Christian religion, apparent in those who consider and estimate time and all things temporal, not by the law and feeling of eternity, but for temporal interests, or from temporal motives, change, or undervalue it, and forget the thoughts and faith of eternity.
[Friedrich von Schlegel, The Philosophy of History, James Baron Robertson, tr. Bohn (London: 1846) pp. 474-475]
Schlegel, of course, was one of the major German Romantic philosophers of the early nineteenth century. His wife Dorothea was the daughter of Moses Mendelssohn, he was roommates with Schleiermacher for a while, he quarreled with Schiller, and he knew many of the major philosophers of the day. He converted to Catholicism in 1808. Philosophie der Geschichte was published in 1829. One of the theses of the book is that one can define a direction of progress in history, and it is in terms of understanding, both speculative and practical, of human beings as being in the image of God, when this is itself worked out historically. One of the things the Zeitgeist does is try to shortcircuit this natural progress, leading Schlegel to reflect that error is always unhistorical and the Zeitgeist is always motivated by passion rather than calm judgment. In particular, it involves a certain kind of idolatry, taking one aspect of the image of God and raising it up as an excuse for every kind of usurpation. The idolatry of the modern age, according to Schlegel, is an idolatry of freedom, which becomes an excuse of perverting reason itself into a kind of partisanship, or expecting it to take its marching orders from the passions of the day.
