What is a Dichotomy?

Mary McMahon
Mary McMahon

A dichotomy is a split into two parts that are considered to be either contradictory or mutually exclusive. The colors black and white are a classic example: either something is black, or it is white, with no room for overlap or alternatives. These divisions are used in a number of ways and in an assortment of fields, from philosophy to biology, and learning to think about them can be important. It is also a good idea for people to learn to identify a false dichotomy — on that is not, in other words, truly mutually exclusive.

A light switch is an example of a dichotomy, as it can either be on or off.
A light switch is an example of a dichotomy, as it can either be on or off.

The word is derived from the Greek dichotomia, which means “splitting in two.” Humans have obviously been using dichotomies for centuries, as they can be valuable tools for quickly identifying things and thinking about the world, although the danger of them is that they can quickly lead to oversimplification. This issue has been a common topic of discussion in many fields for thousands of years.

Dichotomies have been used as keys in the field of Biology, to help with identification.
Dichotomies have been used as keys in the field of Biology, to help with identification.

In biology, dichotomies are often used in keys, tools that are used to help people identify things. For example, a plant key might help people identify plants with a series of questions like “are the stems green?” Such a key is known as a “dichotomous key,” and these tools can be quite reliable when well designed, as they neatly rule out options until the user is left with one solid identification. There are many other applications for these divisions in fields like engineering, astronomy, economics, and so forth, and in some fields the word has a special meaning.

A well known example of a false dichotomy is the saying “you're either with us or against us.” In this case, the saying leaves out a third option, neutrality, setting up an “us vs. them” mentality that can be very dangerous. Such flaws in logic are often used in arguments, in the hopes of brow beating an opponent into conceding a point by forcing the issue. As a general rule, something is a false dichotomy when its elements are not mutually exclusive or contradictory, or when some other option or concept is left out.

Learning to identify these rhetorical tricks in politics can be extremely useful. For example, a politician running for office might say “we need better roads, therefore we need to raise taxes.” This of course leaves out the option of re-allocating existing funds, or of using funds in a more efficient way. The gross-over simplification of the issues is a trait common to many politicians, who want to encourage people to vote for them, along with their policies.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Here's another political fallacy that I don't see mentioned here: "We have to overhaul the health care system or it will add to our deficits!"

Forcing people to buy health insurance or be fined, or force someone to purchase insurance for someone else (people who are taxed and their tax dollars underwriting insurance policies for those that can't afford to purchase insurance) will not bring down our deficits at all, and furthermore it drives up the cost of health insurance for the rest of us.

I see two comments relating to Bush, but the biggest perpetrator of the dichotomy in recent history is barry obama. Anyone who disagrees with me is a fool, and that is no fallacy in reasoning either.


@ Babalaas- Politicians use all kinds of fallacious arguments, and you are right, a skillful politician uses these fallacies with great success. One of the most glaring examples of a false dichotomy or excluded middle fallacy is the argument that sold the patriot act to the people of the United States. It is much easier for a politician to drum up support if you can create the false dilemma that there are only patriots and terrorists.

The argument forced people into a sticky situation. If you fell pray to this false dilemma then you believed either people supported their country or they supported terrorist organizations. There was no option to be an American that enjoyed the right to privacy, yet still loved his or her country.


Politicians often use rhetoric and rhetorical fallacies to create false dichotomies. Some of the best politicians are able to create false dichotomies that trap their opponents, and win over public support. The false dichotomy creates a sense of urgency for the audience. It can be emotionally moving, and create the illusion that there are only two options. When skillfully used, a false dichotomy will make the option the orator supports the most favorable option.

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