"What is this romance?" she mused.
"Ah, that's the question. I've never come across a definition that satisfied me, though there are some very good ones"—he glanced in the direction of his books.
"It's not altogether knowing the other person, perhaps—it's ignorance," she hazarded.
"Some authorities say it's a question of distance—romance in literature, that is—"
"Possibly, in the case of art. But in the case of people it may be—" she hesitated.

Night and Day (1919).