These left me in no doubt that something was trying to communicate with us, but that direct communication would be counterproductive. It seemed to be… - Colin Wilson

Could it be that sexual perversion and romanticism sprang from the same longing for distant horizons?

Behind man lies the abyss, nothingness; the Outsider knows this; it is his business to sink claws of iron into life to grasp it tighter than the indifferent bourgeois, to build, to Will, in spite of the abyss.

This in turn suggests an answer to our question: what happened between the birth of De Sade and the birth of Krafft-Ebbing? The rise of the novel taught Europe to use its imagination. And when imagination was applied to sex, the result was the rise of pornography -- and of "sexual perversion."