A false dichotomy (or black-and-white thinking) is when the possible explanations for an event are arbitrarily reduced to two possibilities. This is a core “tool” for intellectual extremism, since choices are reduced to absolutes. “You’re either with us or against us.” What’s clouded by this fallacy is that there’s a continuum of explanations or possibilities in virtually all scenarios. “Either you believe humans descended from apes or that they were created.” “Actually, humans and apes had a common ancestor so I agree with neither of those positions, though the first is more in line with the evidence.” “You’re either a left- or right-winger.” “Actually, my views on policies are more nuanced than that.” “Which is your favorite meat, chicken or beef?” “There are other meats that exist that I might like to pick from.” “Is this field a science or a pseudoscience?” “There’s a list of things to check off when validating a science, like is it peer-reviewed or is it double-blind or are there independent teams verifying the results, etc. The more you have checked off, the better the science is (as a general rule), so it’s not a black and white choice.”
This fallacy promotes a cartoon view of the world, where the muddy middle has been wiped out of potential consideration. Certainly, when presented with the two extreme options, one can be considered superior over the other. In his essay The Relativity of Wrong, Isaac Asimov made the point that “…when people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.”
This fallacy could be committed on purpose in order to establish a clear party line so as to regulate and enforce a certain way of thinking, with the fear of dissension outweighing the possibility of error. It’s no way to construct a reasoned argument though, no way to have intellectual integrity (which is, in a way, the whole point of scientific skepticism).