syllogism

American  

[sil-uh-jiz-uhm] / ˈsɪl əˌdʒɪz əm /

noun

1. Logic. an argument the conclusion of which is supported by two premises, of which one major premise contains the term major term that is the predicate of the conclusion, and the other minor premise contains the term minor term that is the subject of the conclusion; common to both premises is a term middle term that is excluded from the conclusion. A typical form is “All A is C; all B is A; therefore all B is C.”

2. deductive reasoning.

3. an extremely subtle, sophisticated, or deceptive argument.

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syllogism British  

/ ˈsɪləˌdʒɪzəm /

noun

1. a deductive inference consisting of two premises and a conclusion, all of which are categorial propositions. The subject of the conclusion is the minor term and its predicate the major term; the middle term occurs in both premises but not the conclusion. There are 256 such arguments but only 24 are valid. Some men are mortal; some men are angelic; so some mortals are angelic is invalid, while some temples are in ruins; all ruins are fascinating; so some temples are fascinating is valid. Here fascinating, in ruins, and temples are respectively major, middle, and minor terms

2. a deductive inference of certain other forms with two premises, such as the hypothetical syllogism, if P then Q; if Q then R; so if P then R

3. a piece of deductive reasoning from the general to the particular

4. a subtle or deceptive piece of reasoning

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Etymology

Origin of syllogism

1350–1400; < Latin syllogismus < Greek syllogismós, equivalent to syllog- ( see syllogize) + -ismos -ism; replacing Middle English silogime < Old French < Latin, as above

Explanation

A syllogism is a type of logical reasoning where the conclusion is gotten from two linked premises. Here’s an example: An apple is a fruit. All fruit is good. Therefore apples are good. Used properly, syllogism can be a good way of reasoning, but it’s very easy to make sloppy syllogisms by messing up the middle term that links the premises together, as in: "President Franklin Delano Roosevelt was an Aquarius. President Franklin Delano Roosevelt was great. Therefore all Aquariuses are great." Because so many are made poorly, the syllogism has a bad reputation. Poor, misleading, or tricky reasoning is often called “mere syllogism.”

Example Sentences

It turns out that there are 256 ways to arrange three categorical sentences into a syllogism.

From Salon • Jul. 29, 2024

“My answer to the question is, Abraham Lincoln wrote a syllogism about slavery,” Crow said, holding up a small, handwritten sheet of paper that’s in a protective sleeve, a word or two crossed out.

From Seattle Times • Apr. 17, 2023

This common argument form is called a disjunctive syllogism.

From Textbooks • Jun. 15, 2022

The syllogism he implies is comforting: Only idiots are afraid of sharks; you are not an idiot; therefore you are not afraid of sharks.

From New York Times • May 24, 2022

It worked itself out as simply as a syllogism.

From "I, Robot" by Isaac Asimov