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What is a syllogism?

PhilosophyLesson on requestFree to read

Quick answer

A syllogism is a form of logical reasoning that draws a conclusion from two premises. The classic example: all men are mortal; Socrates is a man; therefore Socrates is mortal. It's a fundamental building block of deductive logic. It has two premises and a conclusion that follows from them.

Key things to understand

  1. It has two premises and a conclusion that follows from them.
  2. If the premises are true and the form valid, the conclusion must be true.
  3. Classic example: All men are mortal; Socrates is a man; so Socrates is mortal.
  4. A valid form can still give a false conclusion if a premise is false.
  5. Aristotle formalized syllogisms over 2,000 years ago.

People also ask

What is an example of a syllogism?
All birds have feathers; a robin is a bird; therefore a robin has feathers — a conclusion forced by the two premises.
Can a syllogism be valid but wrong?
Yes — if a premise is false, the logic can be valid yet the conclusion untrue; valid form guarantees truth only when the premises are true.
Who invented the syllogism?
Aristotle, who systematized this form of deductive reasoning in ancient Greece.