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Four Terms Fallacy / Quaternio Terminorum


Four Terms Fallacy / Quaternio Terminorum

The four terms fallacy is a formal fallacy that covers up the problem when reasoning is based on one of the three fallacies of Agrippa's trilemma. Whenever a logical fallacy is committed, the fallacy has its roots in Agrippa's trilemma. All human thought (without Divine revelation) is based on one of three unhappy possibilities. These three possibilities are infinite regress, circular reasoning, or axiomatic thinking. This problem is known as Agrippa's trilemma. Some have claimed that only logic and math can be known without Divine revelation; however, that is not true. There is no reason to trust either logic or math without Divine revelation. Science is also limited to the pragmatic because of the weakness on human reasoning, which is known as Agrippa's trilemma.

The Four Terms Fallacy / Quaternio Terminorum occurs when a fourth term is introduced into a formal syllogism. This can also happen in informal logic, but it is harder to detect. If we think of a categorical syllogism, there must be three, and only three, terms. They must be unambiguous. The form is something like this: “All S are P. All S are M. All S are P.” Note that there are only three terms; S, P, and M. If the fallacy is committed, a fourth term is introduced. This is often done through equivocation.

Examples of the Four Terms Fallacy / Quaternio Terminorum

“Nothing is more important than love. Crackers and cheese is better than nothing. Crackers and cheese is better than love.”

That was easy, so it’s simple to see what happened. The word, “nothing,” has two meanings, so it introduces the fourth term. Love has several meanings and could fall into the same trap.

“Love fulfills all the Commandments. I want to love you tonight [They are not married.]. I want to fulfill all the Commandments tonight.”

Actually, the second meaning of love doesn’t even have an overlap with the first meaning of love as the two are used in these statements. This is actually a common mistake with the word, “love,” though a syllogism is seldom used, and the logic is usually covered with innuendo or unstated.

“Science is observation. Evolution is observed. Therefore, Evolution is science.”

It sounds good on the surface, and the logical form actually looks good. But let’s examine the reasoning: “Science is observation. Evolution [meaning any changes from generation to generation] is observed. Therefore, Evolution [meaning changes between families of living things such as felidea (cats), rodentia (rodents)] is science.” Now, we can see that it doesn’t make any sense.

Last updated: Sep, 2014
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Toons & Vids



Formally Correct Fallacy / According to the Rules Fallacy (type of)

Logical Fallacy of Affirming the Consequent / Fallacy of the Undistributed Middle Term

Logical Fallacy of Commutation of Conditionals / Fallacy of the Consequent / Converting a Conditional

Logical Fallacy of Affirming a Disjunct / Fallacy of the Alternative Disjunct / False Exclusionary Disjunct / Affirming One Disjunct / Logical Fallacy of the Alternative Syllogism / Asserting an Alternative / Improper Disjunctive Syllogism / Fallacy

Logical Fallacy of Denying the Antecedent / Inverse Error / Fallacy of the Inverse / Invalid modus tollens

Logical Fallacy of Illicit Process

Logical Fallacy of Illicit Major

Logical Fallacy of Illicit Minor

Logical Fallacy of Invalid form using All

Logical Fallacy of Invalid form using "Some"

Logical Fallacy of Unwarranted Contrast / Some Are-Some Are Not

Logical Fallacy of Denying a Conjunct

Logical Fallacy of Negative Premise / Illicit Negative / Drawing a Positive Conclusion from Negative Premises

Logical Fallacy of Drawing a Negative Conclusion from Affirmative Premises / Illicit Affirmative

Logical Fallacy of Existential Instantiation / Existential Fallacy

Fallacy of Exclusive Premises

Logical Fallacy of Four Terms

Logical Fallacy of Necessity / Felacia Necassitas

Logical Fallacy of False Conversion / Illicit Conversion

Logical Fallacy of Illicit Contraposition

Formal Logical Fallacy Illicit Substitution of Identicals / Hooded Man Fallacy / Masked Man Fallacy / Intensional Fallacy / Epistemic Fallacy / Leibniz' Law Fallacy

Formal Logical Fallacy of Confusing "if" with "if and only if"

Logical Fallacy of Negating Antecedent and Consequent / Improper Transposition

Logical Fallacy of Invalid form using "OR"

Logical Fallacy of Confusion of "Necessary" with "Sufficient" Condition

Galileo Wannabe Fallacy / Galileo Argument (Formal)

Four Terms Fallacy / Quaternio Terminorum



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