It is surprising to many that a substantial percentage of science-fiction writers and their hardcore fans are skeptics who do not subscribe to UFO mythologies, cryptozoology, alternative medicines, 9/11 conspiracies or the paranormal.
It seems that the greater the degree of scientific knowledge (in this case a produce of exploring what is plausible though science fiction), the less one quickly believes in the unsubstantiated fantastical. This can be mapped to a curve on the Y axis of credulity that extends along the X axis of scientific knowledge and critical thinking. This lends credence to the idea that a little knowledge is a dangerous thing.
Those who have acquired the basic skills to assess the past and the future in terms of correctly aligned material cause and effect (see chart #1 above) commonly discover that there is little room or need for the introduction of supernatural or quasi-natural causation whether it be karma, fate, god or a hijacked understanding of quantum forces. Their imaginations have not the constraint of material causation, and are therefore susceptible to an infinite number of immaterial causes and possible effects. The arrows of causation are jumbled and misaligned in their minds (see chart #2 above). This unconstrained etiological foundation of their ontology opens them up to suggestions of phenomena that very often follow the fantastic rather than what is possible within the known material web of causation.
This also parallels the curve that maps to the Y axis of faith and the X axis of the depth of understanding of religious texts. Those merely ankle-deep in Christianity often suppose that the Bible is a coherent monolith of consistent and logical doctrine, just as those with a cursory understanding of science and scientific methodology suppose that the literature supporting their pet pseudo-science follows rigorous scientific methodology. However, most of those who have spent a considerable amount of time in the exercise of critical thinking and in the understanding of the web of material causation deny admission to more fantastical ontological candidates that have been contrived without such rigor.
Many of those who have seriously studied the Bible without faith-based assumptions have subsequently rejected it as a source of divine truth due to its many historical, scientific and doctrinal inconsistencies.
However, counter-intuitively, the constraint of scientific methodology, rather than stifling the imagination, actually allows the critical mind to explore the fantastical, but in a domain that in no way bleeds over into reality. A mind so disposed can speculatively plug a “what if” into distant locations outside the the established causal web, assess its plausibility and appreciate the wonder of the fantastical without confusing it with what they know is real. I suggest that this is why the scifi community has more than its share of skeptics.