syllogism
/ SIL-uh-jiz-uhm /
In its classic (categorical) form, a syllogism is a tiny argument with a fixed shape: two starting claims (the premises) lock together to force out a third claim (the conclusion). The classic runs — All men are mortal; Socrates is a man; therefore Socrates is mortal. Think of it as two gears meshing: feed in the right pair and the answer turns out by itself, with no extra push needed.
Its power is that the conclusion is guaranteed. If both premises are true and the shape is valid, the conclusion simply cannot be false — it adds nothing the premises did not already commit you to, and the syllogism just drags that commitment into the open. This is the heart of deduction, and Aristotle was the first to map it out, sorting which shapes are watertight and which only look it.
The common trap: a valid syllogism can still reach a false conclusion if you feed it a false premise. "All birds can fly; a penguin is a bird; so a penguin can fly" follows the rules perfectly — yet it's wrong, because the first premise is false. Validity guarantees the wiring, not the inputs; garbage in, garbage out.
All men are mortal. Socrates is a man. Therefore, Socrates is mortal.
Two premises (one general, one particular) forcing a guaranteed conclusion.
The word comes from the Greek syllogismos, "a reckoning together." Aristotle laid out the theory in his Prior Analytics (4th century BC), and his system of syllogisms reigned as the backbone of logic for over two thousand years, until modern symbolic logic widened the field in the 19th century.