Aby Warburg, lecturing at Hamburg University in the winter of 1927, concluded his reflections on the Nachleben der Antike, the “afterlife of Antiquity,” by comparing two “types of ancient prophet,” Burckhardt and Nietzsche. Both, Warburg said, had been “receivers of mnemonic waves.” Their receptivity to other times and places had resembled that of “sensitive seismographs, which shake in their foundations when they have to receive and transmit the waves.”

There had been, though, a “huge difference” between Burckhardt and Nietzsche. Both had recognized what Warburg called “the violent passions of humans,” and both had “suffered” the “most extreme oscillations” from that recognition. But Burckhardt had “never fully and unhesitatingly affirmed” the suffering or the oscillations. Instead, he had grounded his recognition in rational judgment and remained attuned to “the region of the past.” Nietzsche had spun the dial. Seeking the siren song of the future, he had tuned to the etheric melody of “religious madness” and succumbed to its dangerous “atmosphere of wishing.”

In Warburg’s image, the waves of memory were not watery, like the tidal disturbances of the Homeric sea, or the deep descents of German Romanticism, whether Eduard von Hofmann’s theory of the unconscious as a fathomless dark ocean, or Nietzsche’s wine-dark oblivion, an immolating sunset. They were technical, like radio waves: direct communications from time outside the present, scientific in transmission and reception. This, after all, was 1927: the year of Louis Armstrong’s Hot Five recordings; the year that Mussolini’s regime, completing