Fallacy of Four Terms [#FallacyFridays]
Welcome to #FallacyFridays, the day of the week where learn about flaws in our reasoning. Today’s fallacy is called the fallacy of four terms. Unlike most fallacies, this fallacy is a bit on the more on the technical side. But as always, I will keep it simple to understand.
Make sure to read all the way to the end so that you can test your understanding of the fallacy with the free quiz! 🤓
So in the world of logic, arguments are written in syllogisms (aka statement(s) followed by the conclusion they lead to). Those statements that lead to a conclusion are called premises. Here’s an example:
Premise 1: All humans are mammals.
Premise 2: Trina is a human.
Conclusion: Therefore, Trina is a mammal.
See how writing in syllogisms beautifully shows the progression of an argument? 😍
The example I gave above would be considered a categorical syllogism since it, well, categorizes things (or in this case, people). Categorical syllogisms also have two premises followed by a conclusion.
Since understanding categorical syllogisms will help us understand the fallacy of four terms better, we will briefly discuss more aspects of this syllogism: terms, major and minor premises, and major and minor terms. You will also need to have a bit of grade school English knowledge in mind and know how to identify the subject and predicate of a sentence.
(Here’s a quick example in case you need it:
The subject is followed by the predicate.
Here, “the subject” is literally the subject of the sentence. “Is followed by the predicate” is the predicate.)
Introducing the major and minor premises, major and minor terms, and the middle term.
Now, premise 1 in the first example I gave would be considered the major premise. The major premise contains a term that shows up as the predicate in the conclusion. In this example, that term is “mammal(s)” (which I have put in brackets). I’ve also put the first premise and the conclusion in bold so you can see them clearly:
Premise 1: All humans are [mammals].
Premise 2: Trina is a human.
Conclusion: Therefore, Trina is a [mammal].
Since “mammal(s)” is the term that makes premise 1 the major premise, that makes “mammal(s)” the major term.
On the other hand, premise 2 is the minor premise. The minor premise contains a term that shows up in the subject of the conclusion. In this case, that term is “Trina” (which I have put in brackets). I’ve put the second premise and the conclusion in bold so you can see them clearly:
Premise 1: All humans are mammals.
Premise 2: [Trina] is a human.
Conclusion: Therefore, [Trina] is a mammal.
Since “Trina” is the term that makes premise 2 the minor premise, that makes “Trina” the minor term.
So if we were to rewrite the syllogism again indicating the major and minor premises and major and minor terms, it would look like this:
Major premise: All humans are mammals (the major term).
Minor premise: Trina (the minor term) is a human.
Conclusion: Therefore, Trina (the minor term) is a mammal (the major term).
Now “human(s)” would be considered the middle term since it shows up in both premises but does not show up in the conclusion.
Why having four terms in a syllogism is a logical fallacy
As I was talking about the major and minor premises and terms, you may have noticed that I kept using the word “term.” In logic, terms refer to the nouns, ideas, or qualities mentioned in the syllogism. I’m going to show the syllogism again. But this time, I want you to count how many terms there are:
P1: All humans are mammals.
P2: Trina is a human.
C: Therefore, Trina is a mammal.
How many did you see? If you say you saw three of them, you got it right! The three terms are human(s), mammal(s), and Trina.
Now let’s try to bring a fourth term into the mix. In fact, we’ll make sure this term has a similar vibe to human, mammal, and Trina. Let’s make “living organism” our fourth term and fit it into this syllogism like so:
P1: All humans are mammals.
P2: Trina is a human.
C: Therefore, Trina is a living organism.
But wait a minute.
Now with that fourth term, there is a disconnect. Sure, mammals, humans, and Trina are all organisms. But they are not all necessarily living organisms. For all we know, Trina could be dead. The premises All humans are mammals and Trina is a human do not automatically lead to the conclusion that Trina is a living organism.
The fallacy of four terms often makes the mistake of assuming that certain terms are interchangeable or are used the same way when they not. This is called equivocation.
Here, the main equivocation was “mammals” with “living organism.” But, just as Trina is not necessarily the same as “living organism,” “mammals” aren’t necessarily the same thing as “living organisms.”
No matter where we place “living organisms” in the syllogism, it will still be the four terms fallacy.
The fallacy of four terms often makes the mistake of assuming that certain terms are interchangeable or are used the same way when they not. Click To TweetQuick Exercise
To see how “living organisms” looks elsewhere inside of the syllogism, replace only one the term in brackets with “living organisms.” For example,
All [humans] are [mammals].
Trina is a [human.]
Therefore, Trina is a [mammal].
…can become…
All living organisms are mammals.
Trina is a human.
Therefore, Trina is a mammal.
No matter which single term you replace, it is still a four terms fallacy.
Fallacy of four terms in everyday use
Obviously, we don’t speak in syllogisms in everyday life. When we state our arguments in our everyday conversations, we tend to introduce our conclusion first and then follow with the premises.
So instead of saying…
All humans are mammals.
Trina is a human.
Therefore, Trina is a mammal.
We would say…
Trina is a mammal because she is a human and all humans are mammals.
Now, if we introduced a fourth term into the mix, the everyday version of this four terms fallacy would go from…
All humans are mammals.
Trina is a human.
Therefore, Trina is a living organism.
…to this:
Trina is a living organism because she is a human and all humans are mammals.
Regardless of how you put it–whether in the form of a syllogism or in the way we speak outside of a logic class–the premises do not support the conclusion.
Here’s another example:
Kehinde has charisma because he looks funny. Plus, people with a knack for comedic timing have charisma.
In the syllogistic form, it looks like the following:
People with a knack for comedic timing have charisma.
Kehinde looks funny.
Therefore, Kehinde has charisma.
The four terms in this example are “People with a knack for comedic timing,” “charisma,” “looking funny” and “Kehinde.” Now, it may not have been obvious in the “everyday” form. In fact, this case of equivocation is quite sinister. “Looking funny” may have the word “funny” in it, but that phrase is not a measure of comedic timing. If you say someone looks funny, you’re saying they look weird. Unattractive even. It doesn’t even remotely imply comedic talent.
Pro-Tip: Just like the case of the non sequitur fallacy, when faced with a possible case of the four terms fallacy, make sure it is in syllogistic form first to determine if it is indeed fallacious. This way, it is much easier to see if there are four terms and if the premises actually do (or do not) flow to the conclusion.
RELATED: The Non Sequitur Fallacy.
Quiz Time!
Only one of the following answer choices contains the fallacy of four terms. Which one is it?
A. Kaleb is definitely a scientist because he is curious and those who are curious tend to be scientists.
B. Jen knows how to do archery.
Archery is a skill one performs.
Therefore, Jen knows how to perform a skill.
C. Justine is gullible because she gossips often and people that gossip often don’t mind their own business.
D. Dancing is important to me because it makes me happy and being happy is important to me.
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