Defining Science Fiction

George Hay ("futurologist")    
Brian Aldiss (science fiction writer)    
H. G. Wells (polymath)    
Eric Rabkin (tri-partite definition)    
Frederic Brown (science fiction writer)    
Eric Rabkin (theoretical definition)    

George Hay:

"Science fiction is what you find on the shelves in the library marked science fiction."

  robot-thinker