Mister Fandango wrote:
"Psionics" was just a means of giving magic a scientific explanation and terminology. The only real difference between a psychic and a wizard is one wears robes and a funny hat.
First, people like John W. Campbell really did believe, at least for a while (then maybe were too stubborn to retreat) there could be a real science/tech of "psionics." In this kind of thinking, "psychics" were naturally gifted but later everyone would be able to buy psychic abilities at a Radio Shack or Lowe's. The difference between that kind of psychic and a wizard is not just the clothing.
Second, although many stories are adventure stories and wish fulfilment, where the difference between SF and fantasy modes is purely stylistic, there are in fact SF stories which do depend upon the speculations in a way that is incompatible with fantasy.
Olaf Stapledon can't be rewritten as a fantasy, Jules Verne can't be rewritten as a fantasy and H.G. Wells can't be rewritten as a fantasy.