It has been suggested that SF include only those stories which would be invalidated without their scientific content;  that fiction which concerns science, scientists, and the impact of science on humans;  that which explores alternate existences (whether future, extraterrestrial, or only in characters' minds) based on facts and logical progression via scientific method.
( It ( ( has ( been ( suggested ( that ( SF ( include ( ( ( ( ( ( ( ( only ( those stories ) ) ( which ( would ( be ( invalidated ( without ( their ( scientific content ) ) ) ) ) ) ) ) ; ) ( ( that fiction ) ( which ( ( concerns ( ( ( ( ( science , ) scientists ) , ) and ) ( ( the impact ) ( of science ) ) ) ) ( on humans ) ) ) ) ) ; ) ( that ( which ( ( ( explores ( alternate existences ) ) ( -LRB- ( ( ( ( ( ( ( whether future ) , ) extraterrestrial ) , ) or ) ( only ( in ( ( characters ' ) minds ) ) ) ) -RRB- ) ) ) ( based ( on facts ) ) ) ) ) ) and ) ( ( logical progression ) ( via ( scientific method ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ has) (VP (VBN been) (VP (VBN suggested) (SBAR (IN that) (S (NP (NNP SF)) (VP (VBP include) (NP (NP (NP (RB only) (DT those) (NNS stories)) (SBAR (WHNP (WDT which)) (S (VP (MD would) (VP (VB be) (VP (VBN invalidated) (PP (IN without) (NP (PRP$ their) (JJ scientific) (NN content))))))))) (: ;) (NP (NP (DT that) (NN fiction)) (SBAR (WHNP (WDT which)) (S (VP (VBZ concerns) (NP (NP (NN science)) (, ,) (NP (NNS scientists)) (, ,) (CC and) (NP (NP (DT the) (NN impact)) (PP (IN of) (NP (NN science))))) (PP (IN on) (NP (NNS humans))))))) (: ;) (NP (NP (DT that)) (SBAR (WHNP (WDT which)) (S (VP (VBZ explores) (NP (JJ alternate) (NNS existences)) (PRN (-LRB- -LRB-) (NP (NP (IN whether) (JJ future)) (, ,) (NP (JJ extraterrestrial)) (, ,) (CC or) (NP (NP (JJ only)) (PP (IN in) (NP (NP (NNS characters) (POS ')) (NNS minds))))) (-RRB- -RRB-)) (PP (VBN based) (PP (IN on) (NP (NNS facts)))))))) (CC and) (NP (NP (JJ logical) (NN progression)) (PP (IN via) (NP (JJ scientific) (NN method))))))))))) (. .)))
Some people think Science Fiction should necessarily espouse facts and logic rooted in the scientific method.
( ( Some people ) ( ( think ( ( Science Fiction ) ( ( should necessarily ) ( espouse ( ( ( facts and ) logic ) ( rooted ( in ( the ( scientific method ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT Some) (NNS people)) (VP (VBP think) (SBAR (S (NP (NNP Science) (NNP Fiction)) (VP (MD should) (ADVP (RB necessarily)) (VP (VB espouse) (NP (NP (NNS facts) (CC and) (NN logic)) (VP (VBN rooted) (PP (IN in) (NP (DT the) (JJ scientific) (NN method)))))))))) (. .)))