A false dilemma is an informal fallacy based on a premise that erroneously limits what options are available.
[3][4][1][5] The problematic content in the case of the false dilemma has the form of a disjunctive claim: it asserts that one among a number of alternatives must be true.
[1] In its most common form, a false dilemma presents the alternatives as contradictories, while in truth they are merely contraries.
Two propositions are contraries if at most one of them can be true, but leaves open the option that both of them might be false, which is not possible in the case of contradictories.
A common form of using contraries in false dilemmas is to force a choice between extremes on the agent: someone is either good or bad, rich or poor, normal or abnormal.
In their most simple form, they can be expressed in the following way:[7][6][1] The source of the fallacy is found in the disjunctive claim in the third premise, i.e.
The following is an example of a false dilemma with the simple constructive form: (1) "If you tell the truth, you force your friend into a social tragedy; and therefore, are an immoral person".
[1] This example constitutes a false dilemma because there are other choices besides telling the truth and lying, like keeping silent.
Lewis's trilemma is a famous example of this type of argument involving three disjuncts: "Jesus was either a liar, a lunatic, or Lord".
[8] In the case of a defeasible false dilemma, the support provided for the conclusion is overestimated since various alternatives are not considered in the disjunctive premise.
[9][1] In the case of the false dilemma, the tendency to simplify reality by ordering it through either-or-statements may play an important role.
In order to avoid false dilemmas, the agent should become aware of additional options besides the prearranged alternatives.
[10] An exception is analytic philosopher John Searle, who called it an incorrect assumption that produces false dichotomies.
The presentation of a false choice often reflects a deliberate attempt to eliminate several options that may occupy the middle ground on an issue.
This argument assumes that, for example, a bar must be shut down to prevent disturbing levels of noise emanating from it after midnight.