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

Syllogism One night last week there was a rosy sunset in Manhattan.

From Time Magazine Archive

Syllogism In Chicago, dismissing the complaint of Fruiterer Allen Brill that Customer A. E. Banks had hit him on the head with twelve melons.

From Time Magazine Archive

The main use of the Syllogism is in dealing with incompletely expressed or elliptical arguments from general principals.

From Logic, Inductive and Deductive by Minto, William

It has often been argued that the Syllogism involves a petitio principii, because the Major Premiss contains the Conclusion, and would not be true unless the Conclusion were true.

From Logic, Inductive and Deductive by Minto, William

The Syllogism merely shows the interdependence of premisses and conclusion; its only tacit assumption is the Dictum de Omni.

From Logic, Inductive and Deductive by Minto, William