We reduce an issue to “either A or B”. Then, by denying “A”, we conclude that “B” must be true, without considering that the dichotomy may be false or incomplete and that other options may also exist.
Definition:
This fallacy occurs when someone bases their reasoning on an “either … or …” (disjunctive) proposition and, by denying one of the two options, concludes that the other must be true.
In formal logic, if the premises are true, this form of reasoning is valid[1]. However, in practice, the same seemingly valid structure is often used to deceive and turns into a fallacy, because either the premises are false or the real options have been deliberately limited. For example:
“Either I must always stay at home or always be outside. Since I do not want to always stay at home, I must always be outside.”
Here, it should be noted that other choices, such as sometimes staying at home and sometimes going out, also exist.
The typical structure of this fallacy:
1. The claimant says: Either “A” or “B”.
2. Then adds: “Not A!”.
3. Concludes: Therefore, “B” is true.
Examples from real life:
1. In politics:
“Either we must support this party or the enemies of the country will prevail. Since we cannot strengthen the enemies, we must support this party.”
Here, it should be noted that the flaw in this reasoning is that it presents only two options, whereas other possibilities, such as creating a new party or reforming the existing political structure, also exist.
2. In the media:
“Either we must accept all new technologies or we will be backward and ignorant. Since ignorance is unacceptable, we must accept every new technology without question.”
Here, it should be noted that selective and critical acceptance of technologies is also a real option, which has been omitted either deliberately or inadvertently.
3. In the family:
“Either we must enrol the child in numerous private classes or they will fail in the future. Since we do not want their failure, we must accept the private classes.”
Here, it should be noted that balanced upbringing and formal education can also provide a successful future.
4. In international politics:
“Either we must lift all sanctions on that rogue state or war will be inevitable. Since we do not want war, all sanctions must be lifted.”
Here, it should be noted that other solutions, such as limited negotiations, phased agreements, or encouraging changes in that country’s domestic and foreign policies, are also possible.
5. In education and schooling:
“Either pupils must spend hours every day doing homework or they will not learn anything at all. Since illiteracy is unacceptable, heavy homework must continue.”
Here, it should be noted that a variety of teaching methods, such as active learning or project-based learning, also exist.
6. In religion and ethics:
“Either all the commands of traditional religion must be followed unquestioningly or society will become immoral. Since we do not want immorality, we must accept everything as it is.”
Here, it should be noted that morality can move beyond the confines of rigid religious tradition and be grounded in the Universal Declaration of Human Rights. Such morality is secular and universal.
7. In social and personal relations:
“Either you must always be with your friends or it shows that you are their enemy. Since enmity is bad, you must be with them whenever they want.”
Here, it should be noted that friendship can take different forms, and being with others all the time is not the only measure of loyalty.
8. In social media and the press:
“Either we must accept all the news as it appears on social networks or we will remain ignorant of the world. Since ignorance is harmful, we must trust every piece of news on social media.”
Here, it should be noted that consulting reliable sources and professional journalism are also real options to avoid being uninformed.
Why is this fallacy dangerous?
- It appears logical and sound, because it employs a valid logical structure.
- It forces the audience to choose only between two limited options.
- It eliminates the possibility of critical discussion about hidden or excluded alternatives.
- In politics and the media, it is a powerful tool for persuasion and for imposing flawed decisions.
How can we recognise and respond to it?
If we see that an argument is based only on a false dichotomy, or uses the denial of one part to reject the other, we should ask:
– “Does your ‘either … or …’ really cover all the options, or have you deliberately reduced it to only two?”
– “Is there really no third possibility?”
A suitable response might be: “You have assumed that only two options exist, whereas other choices may also be possible.”
Conclusion:
The Denying a Disjunct Fallacy appears convincing and persuasive because it employs the correct logical form. Its danger, however, lies in the fact that by eliminating or distorting real alternatives, or by hastily concluding from the denial of one option, it directs the mind towards a predetermined outcome.
[1] In formal logic, the argument “either A or B; not A; therefore B” is valid. However, when the “either … or …” is restricted or distorted, or the premises are fundamentally false, the use of this reasoning turns into a fallacy.