A false dilemma (also called black-and/or-white thinking, bifurcation, denying a conjunct, the either-or fallacy, false dichotomy, fallacy of exhaustive hypotheses, the fallacy of false choice, the fallacy of the false alternative, or the fallacy of the excluded middle) is a type of informal fallacy that involves a situation in which limited alternatives are considered, when in fact there is at least one additional option. The opposite of this fallacy is argument to moderation.
The options may be a position that is between two extremes (such as when there are shades of grey) or may be completely different alternatives. Phrasing that implies two options (dilemma, dichotomy, black-and-white) may be replaced with other number-based nouns, such as a “false trilemma” if something is reduced to only three options, instead of two.
False dilemma can arise intentionally, when fallacy is used in an attempt to force a choice (such as, in some contexts, the assertion that “if you are not with us, you are against us”). But the fallacy can also arise simply by accidental omission of additional options rather than by deliberate deception.