When a syllogism uses four terms instead of the three logical ones (minor, major, and middle), the logical connection between the premises and the conclusion is lost. This error typically arises from using a word with two different meanings or introducing another term.
Definition:
In a valid syllogism, there must be exactly three terms. The fallacy of four terms occurs when:
– A word is used with a different meaning in each premise (ambiguity or equivocation).
– Or a new word is introduced that breaks the link between the premises and the conclusion.
– As a result, the argument looks logical, but is invalid. For example:
“Every star has light.
A film star also has light.
Therefore, a film star is the same as a celestial star.”
Here, it should be noted that the word “star” in the first premise means a celestial body, while in the second it means a famous person in cinema. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
Typical structure of this fallacy:
- First Premise: All A are B.
- Second Premise: All C are D.
- Conclusion: Therefore, all A are D.
On the surface there seem to be three terms, but since B and C are different, the syllogism ends up with four terms.
Examples from real life:
1. A classic example in logic:
“Every law must be obeyed.
The law of conservation of energy is a scientific principle.
Therefore, the law of conservation of energy must be obeyed.”
Here, it should be noted that the word “law” in the first premise means a social rule or regulation, while in the second it means a scientific principle. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
2. In domestic politics:
“Democracy means the rule of the people.
Today elections are being held.
Therefore, democracy is established.”
Here, it should be noted that the word “democracy” in the first premise means the true sovereignty of people over their destiny, while in the second it means only the holding of elections. This change in meaning gives the syllogism four terms, so the conclusion is invalid. Moreover, true democracy is not achieved by voting alone; it also requires wise, well-educated candidates, in line with Article 26 of the Universal Declaration of Human Rights, so that voters’ rights are not violated.
3. In the media:
“Every piece of news that is real is worthy of trust.
Every piece of news published by the state media is real.
Therefore, every piece of news published by the state media is worthy of trust.”
Here, it should be noted that the word “real” in the first premise means matching external reality, while in the second it means official publication by state media. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
4. In the family:
“Anyone who cares for their child sends them to school.
You do not send your child to a private school.
Therefore, you are not caring.”
Here, it should be noted that the word “school” in the first premise means formal education in general, while in the second it is limited to “private school”. This change in meaning gives the syllogism four terms instead of three, so the argument is invalid.
5. In public relations and advertising:
“Every authentic product must have a historical origin.
This brand is renowned for the authenticity of its raw materials.
Therefore, this brand has a historical origin.”
Here, it should be noted that the word “authenticity” in the first premise means age and historical roots, while in the second it refers to the quality or purity of raw materials. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
6. In economics:
“Every investment must be profitable.
Investment in education is highly beneficial.
Therefore, education must make money.”
Here, it should be noted that the word “profit” in the first premise means financial return, while in the second it means social and moral benefit. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
7. In science and technology:
“Every theory must be supported by empirical evidence.
So-and-so has a theory about his new film.
Therefore, his theory is supported by empirical evidence.”
Here, it should be noted that the word “theory” in the first premise means a scientific model based on evidence, while in the second it means a guess or personal opinion. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
8. In the workplace:
“Every good employee must be punctual.
He is renowned for his punctuality in public speeches.
Therefore, he is a good employee.”
Here, it should be noted that the word “punctuality” in the first premise means being on time and keeping to working hours, while in the second it means managing time in speeches or keeping to programme time limits. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
9. On social media:
“Everything that is important must be paid attention to.
Everything that trends on the internet is important.
This rumour trended on the internet.
Therefore, this rumour must be paid attention to.”
Here, it should be noted that the word “important” in the first premise means real value and tangible impact, while in the second it means temporary popularity or visibility online. This change in meaning gives the syllogism four terms, so the conclusion is invalid.
Why is this fallacy dangerous?
- Concealment: The error hides within linguistic ambiguity and is difficult for the public to detect.
- Disruption of dialogue: Ambiguous words divert the discussion from its main course.
- Political and advertising misuse: Great concepts such as “freedom”, “justice”, or “democracy” are turned into tools of deception through shifts in meaning.
How can we recognise it and respond?
Check whether the words in the premises and the conclusion are used in exactly the same sense, and then ask:
– “Does this word have one or multiple uses?”
– “Is its meaning the same everywhere and across all uses?”
– “Has it taken on a new meaning in each of your premises?”
A suitable response might be: “In your argument, a word is used in two different senses. This shift gives the syllogism four terms, so the conclusion is invalid.”
Conclusion:
The fallacy of four terms shows that linguistic precision is the foundation of logical reasoning. The practical aspects of each word in every field must be clearly defined, and its meaning in every context must be completely clear [1]. If the meaning of words changes across different contexts, the argument loses its validity and slips from reasoning into fallacy. Recognising the fallacy of four terms helps us avoid being deceived by linguistic tricks and ensures that concepts such as “democracy” or “freedom” are used in their precise sense, consistent with human rights, rather than in a distorted or propagandistic way.
[1] True philosophy, unlike academic philosophy, is based on clear definitions of concepts. This approach not only distinguishes “law” in physics from “law” in society, but also, by clearly distinguishing between “law” and “non-law”, prevents the misuse of the term “law”, just as it distinguishes true democracy from mere ballot-box voting or the tyranny of the majority.
Understanding true philosophy helps us prevent such abuses and ensures that human rights are properly upheld.