False Dilemma


The argument either misrepresents the consequences of choices that are available when making a decision, or else it fails to present all the choices available.



The term "dilemma" originally meant an argument with two major premisses (hence two "lemmas"). It has come to mean an argument made up of two hypothetical statements, and a choice between their antecedents. The classic structure of a dilemma can be represented as follows:

                    If A, then B.
                    If C, then D.
                    Either A or C.
                    So, either B or D.

The argument is defined by this structure rather than (as with other fallacies) the nature of the error. Hence, it can be classified in different ways, depending upon whether the error is in one of the "if" statements (in which case the fallacy is a Misrepresentation) or in the "or" statement (in which case the fallacy is an Irrelevancy, in the family that I call the Middle Ground fallacies). The fallacy is traditionally called "false dilemma" regardless of where the error occurs. This is the only fallacy on my list that received double classification. (By the way, while the word "lemma" means "major premiss," and refers to the two "if" statements, by my analysis the "if" statements are actually minor premisses. The major premiss is the "or" statement.)



"If we completely cut off military funding for Egypt, we risk breaking an old alliance. If we continue to fund the Egyptian military, we violate our own law against supporting a military coup. We must either cut off the funding or we must continue the funding. Hence we must either risk breaking an old alliance or we must violate our own laws."


"If the university builds a new library, we will have to raise tuition to cover costs and enrollment will drop. If we don't build a new library we could lose our accreditation and enrollment will definitely suffer. Either way, I wouldn't plan on our enrollment increasing next year."



In a dilemma, as the word is popularly understood, every possible course of action has undesirable consequences. We are in a "no win" situation: screwed no matter what we do. Of course, not all dilemmas are false. In some cases there really are no good options. The fallacy of False Dilemma has the same formal structure as a "true" dilemma, so it is easy to mistake the one for the other.

However, when a dilemma is fallacious, it can be defeated in one of two ways:

Going between the horns - showing that the alternative courses of action are not exhaustive, and that some unstated alternative does not have undesirable consequences. In the above example, maybe we could suspend military funding temporarily, rather than cutting it off completely, which would maintain the alliance while still being in compliance with the law against supporting a coup.

Seizing one of the horns - showing that the supposedly undesirable consequences of one of the alternatives either does not follow at all, or is not really undesirable. In the above example, perhaps cutting off military funding would not result in a breach of the alliance...or, perhaps breaking the alliance would actually not be a bad thing. Alternatively, perhaps the military takeover was not really a "coup," so a continuation of funding is legal.

When the error is discovered by "going between the horns," then the argument is a deductive irrelevancy, obviously in the family of Middle Ground fallacies, somewhat similar to Black & White Thinking. When the error is discovered by "seizing one of the horns," then the argument is a deductive Misrepresentation.


Source: The phrase "false dilemma" is in common usage on the Internet. However, I am unable to identify an earliest classical print source for the fallacy.


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