Lexicon Subtleties: Syllogism

Blog entry # 85

What is syllogism?

Popularized by Aristotle, syllogism is a logic-based argument where a conclusion is deduced from the combination of a general statement and a specific statement. If you’ve studied logic in school or college, you’d be familiar with modus ponens: P implies Q and P is true, therefore Q must be true.

What are the types of syllogism?

• Conditional Syllogism: If A is true then B is true (If A then B).
• Categorical Syllogism: If A is in C then B is in C.
• Disjunctive Syllogism: If A is true, then B is false (A or B).

Why syllogism?

It is a tool in the hands of a speaker or a writer to persuade the audience. This is because their belief in a general truth may tempt them to believe in a specific conclusion drawn from those truths.

Examples of syllogism

General: "Every virtue is laudable; kindness is a virtue; therefore kindness is laudable."

Aristotle: “All men are mortal. Socrates is a man. Therefore, Socrates is mortal.”

In advertising: “With a name like Smucker’s, it has to be good.” —Smucker’s jams

René Descartes: "Cogito ergo sum" ("I think, therefore I am.")

William Shakespeare: The Merchant of Venice
"Who chooseth me shall gain what many men desire."
Why, that’s the lady. All the world desires her.

George Orwell: Animal Farm
"All animals are equal, but some animals are more equal than others."

Syllogistic Fallacies

Dogs are animals; all dogs have four legs; hence all animals have four legs.