sentence1: 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.
sentence2: Many Science Fiction stories are wholly unscientific and should instead be categorized as Fantasy and false is not true .