The world's greatest lovers were undoubtedly Mellius and Gretelina, whose pure, passionate and soul-searing affair would have scorched the pages of History if they had not, because of some unexplained quirk of fate, been born two hundred years apart on different continents.
-- Terry Pratchett, Mort
I just realized I haven't previously pointed the metaphysicians on Less Wrong to "Possible Girls," a hilarious paper about acausal romance:
Even if you don't read the whole thing, don't miss the final paragraph.