This article is from the rec.arts.sf.written FAQ, by Evelyn C. Leeper evelynleeper@geocities.com with numerous contributions by others.
See Q#7.
This also has been done to death. Virtually every answer you give will
fail to clearly indicate which category a large number of books belong
to. Familiar books mentioned that test the boundary conditions include
Anne McCaffrey's "Dragon" series, Piers Anthony's "Apprentice Adept"
series, STAR WARS, and anything that uses FTL. The most concise
definition I've heard was given by John Clute in a radio broadcast 22
March 1997: " "Science fiction: the model is that it is a kind of story
which argues from this world a kind of possible outcome. It's possibly
an improbable outcome, but it is arguable. Fantasy essentially, as I
have been seeing it, is a series of stories, self-coherent stories (a
term we use, kind of a bad neologism to describe stories which as [it]
were understand themselves as stories; they're told stories), that are
set in worlds that are technically impossible, that we can't argue. We
may believe in them, but we can't argue them."
A more complete listing of the borderline cases includes:
Poul Anderson's "Operation" stories, collected in OPERATION CHAOS
Piers Anthony's "Apprentice Adept" series
James Blaylock's "Elfin Ship"
Marion Zimmer Bradley's "Darkover" series
David Brin's PRACTICE EFFECT
Rick Cook's "Wizard's Bane" series
L. Sprague de Camp & Fletcher Pratt"s "Incomplete Enchanter" series
Charles de Lint's SVAHA
C. S. Friedman's "Coldfire" series
Lyndon Hardy's "Master of the Five Magics" series
Robert A. Heinlein's MAGIC, INC.
Rosemary Kirstein's STEERSWOMAN and THE OUTSKIRTER'S SECRET
Julian May's "Pliocene Exile" series
Anne McCaffrey's "Dragonrider" series
Walter M. Miller's CANTICLE FOR LEIBOVITZ
James Morrow's THIS IS THE WAY THE WORLD ENDS
Kristine Kathryn Rusch's ALIEN INFLUENCES
Robert Silverberg's "Majipoor" series
Christopher Stasheff's "Warlock" series
Michael Swanwick's IRON DRAGON'S DAUGHTER
Sheri Tepper's "The World of the True Game" books
Lawrence Watt-Evans's "Three Worlds" series
Lawrence Watt-Evans's CYBORG AND THE SORCERERS and THE
WIZARD AND THE WAR MACHINE
Walter Jon Williams's METROPOLITAN and CITY ON FIRE
Gene Wolfe's "Book of the New Sun"
Roger Zelazny's LORD OF LIGHT
(anything with faster-than-light (FTL) travel, time travel,
parallel worlds/universes, psionics, or shoddy science)
(Often someone suggests that fantasy and science fiction can be easily
divided and this list is brought up, the original poster responds by
saying they haven't read any of these so they can't say which category
they go in. This is not likely to convince people that such a division
is possible. :-) )
Of course, you can also check out Jerry Oltion's essay on this in the
March 1997 issue of THE MAGAZINE OF FANTASY & SCIENCE FICTION.
[Provided by Evelyn Leeper [evelynleeper@geocities.com].]
 
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