A false dilemma fallacy is a logical fallacy in which a limited number of possible options are presented when, in truth, more options may be available. Such a fallacy might suggest that one needs to choose between "A" and "B," when in fact choices "C" and "D" are also perfectly valid. In many cases, this argument presents two choices at the extremes of the possible options, thereby omitting a range of possibilities between the extremes. In such cases, the false dilemma fallacy is often referred to as the "excluded middle fallacy." Many times, such a fallacy is used to present one option that is clearly better than the other in order to make the better option in the argument seem like the best option overall.
It is important to be able to identify a false dilemma fallacy if one does not wish to fall for the fallacious argument. Upon being given a limited number of possibilities in an argument or theoretical situation, one should ask oneself if the given options are, indeed, the only viable or logically possible options. If they are not, a false dilemma fallacy is being used and the argument is invalid. Suggesting other options forces the person who used the fallacy in the first place to clarify his ideas and to explain why he only chose a few specific options.
Not all cases in which a limited number of options are given are actually fallacious. For instance, stating that a person is either dead or alive is not a false dilemma fallacy, as there is no state existing between life and death — there is no third option. Stating that a person is either "good" or "evil," on the other hand, is fallacious because there is a whole spectrum existing between good and evil. Such a false dilemma fallacy leads to the notion that if someone is not wholly good, he is necessarily evil, and vice versa.
There are many uses for the false dilemma fallacy. This type of argument can be used to drive people toward a certain opinion or course of action by comparing the arguer's opinion or proposed course of action with a clearly harmful one. Advertisers also make use of the false dilemma fallacy in order to suggest that their products are necessary for avoiding a bad outcome of some sort. A false dilemma may be used, for instance, to suggest that if one does not own a certain type of mop, one will certainly have dirty floors — this is fallacious because a wide range of other cleaning products could be used to clean one's floors.