The Black-or-White Fallacy


Taxonomy: Logical Fallacy > Informal Fallacy > The Black-or-White Fallacy


Gerda Reith is convinced that superstition can be a positive force. "It gives you a sense of control by making you think you can work out what's going to happen next," she says. "And it also makes you feel lucky. And to take a risk or to enter into a chancy situation, you really have to believe in your own luck. In that sense, it's a very useful way of thinking, because the alternative is fatalism, which is to say, 'Oh, there's nothing I can do.' At least superstition makes people do things."5



See the See the Technical Appendix, below.


The black-or-white fallacy occurs only in arguments that have a disjunctive premiss―that is, a premiss of the "either-or" form that gives alternatives. The fallacy is committed when a disjunct―that is, an alternative―is incorrectly omitted. The fallacy tries to force you to choose either black or white when gray is an available alternative.


This is one of the favorite fallacies of extremists, and many public debates on political and moral issues are polarized by those who use it to try to force others to the extremes. For instance, the debate over the legal and ethical status of abortion is dominated by extremists who either oppose all abortions without exception, or favor the permissibility of abortion up to the point of birth.

Now, I'm not taking a position on this issue; I'm just pointing out that most people take neither extreme position. Most people think that some but not all abortions are morally permissible, and should be legally permissible as well. Maybe they're wrong, but differences of opinion on this issue are almost always over where on the spectrum from conception to birth to allow legal abortions.

The extremists are as far apart as possible on this and other issues, and they hate each other. Most of the rest of us are trapped in between, but often closer to each other than we realize. For democracy to work as it is supposed to, people must be able to meet those they disagree with and address issues with reason, not violence. The extremists will never come together except to fight. This is why a political environment that is polarized to the extremes is a danger to democracy.

Analysis of the Example:

Fatalism is not the alternative to superstition; it is an alternative. Superstition involves acting in ways that are ineffective, whereas fatalism involves failing to act even in situations in which our efforts can be effective. Fortunately, there are other alternatives, such as recognizing that there are some things we can control and other things we cannot, and only acting in the first case.

Notice the claim in the Example that "the alternative" to superstition "is fatalism". Beware of the phrase "the alternative" as there is seldom a single alternative available. If you hear that "the" alternative to some view or action is something unpleasant or obviously false, always ask: "Are there other alternatives? What are they?" The phrase "the alternative" is often a tip-off that a black-or-white fallacy is coming up.

Technical Appendix:

The Black-or-White Fallacy is a seemingly paradoxical fallacy in that it is a validating form of argument, that is, every instance of it is valid. It is, however, not the only informal fallacy with this surprising characteristic as Begging the Question is also validating. For example, some instances of the Black-or-White Fallacy have the familiar validating form:

Disjunctive Syllogism Simple Constructive Dilemma
Either p or q.
Therefore, q.
Either p or q.
If p then r.
If q then r.
Therefore, r.

The second form gives the fallacy its names of "bogus" or "false" dilemma. The dilemma is "bogus" or "false" because the disjunctive premiss does not include every alternative.

The seeming paradox of a valid fallacy can be dispelled by realizing that validity isn't everything: a good argument must also have true premisses, that is, it must be sound. Usually, however, the truth or falsity of premisses is not a question for logic, but for other sciences, or even common sense. So, while an argument with a false premiss is unsound, it is not usually considered to be fallacious6. However, when a disjunctive premiss is false for logical reasons, then the argument does commit a fallacy.

One such logical error is confusing contrary with contradictory propositions: given two contradictory propositions, exactly one will be true; but given two contrary propositions, at most one will be true, but both may be false. For example: "It's hot today" and "It's not hot today" are contradictories, whereas "It's cold today" and "It's hot today" are contraries, since it might be between cold and hot, say, warm or cool.

A disjunction whose disjuncts are contradictories is an instance of the Law of Excluded Middle, so it is logically true. For instance, "either it's hot today or it's not hot today." In contrast, a disjunction whose disjuncts are contraries is logically contingent. For example, "either it's hot today or it's cold today." An arguer who confuses contraries with contradictories in the premiss of an argument commits the Black-or-White Fallacy.


  1. This fallacy is known by an unusually large number of names. I prefer "black-or-white fallacy" because it best describes the nature of the logical mistake underlying it. See S. Morris Engel's With Good Reason: An Introduction to Informal Fallacies (6th Edition) (St. Martin's, 2000), pp. 144, 153-6 & 302, for all of these aliases except "black-and-white fallacy" and "false dichotomy", but including "black-or-white fallacy".
  2. Peter A. Angeles, Dictionary of Philosophy (2000), see under "Fallacy, types of informal (1)".
  3. Madsen Pirie, How to Win Every Argument: The Use and Abuse of Logic (2015), pp. 24-26.
  4. Nigel Warburton, Thinking A to Z (2nd edition, 2000).
  5. David Newnham, "Hostages to Fortune", The Guardian, 12/13/2002.
  6. Some logicians do include an entire category for fallacies of false or questionable premisses in order to have a place for this fallacy and begging the question. For an example, see Engel, Note 1, above, who calls this category "fallacies of presumption" (Chapter 4).

Revised: 5/9/2022