Syllogica

Each round gives you two premises and several candidate conclusions. Exactly one follows validly; the rest are traps, and each one is broken in a specific, named way rather than being merely wrong. Your job is to pick the conclusion the premises actually support.

• Validity here is about form, not truth — a conclusion can be factually true and still not follow.
• The decoys are classical fallacies: undistributed middle, illicit major, illicit minor, drawing an affirmative conclusion from a negative premise, and existential assumptions.
• Every puzzle is generated so that exactly one option is valid, so there is always a right answer.
• The same seed always produces the same round.

• Desktop: click region tiles and conclusion options; some choices are keyboard-accessible too
• Phone & tablet: tap tiles and answers, fully touch-driven

• Daily: the same arguments for everyone each day
• Practice: fresh arguments every run
• Easy, Medium and Hard add subtler fallacies and more terms

• Ignore whether the statements sound true. The commonest error is choosing the conclusion that matches the world rather than the one that follows from the premises.
• Check the middle term first. If the term linking the two premises is never used universally in either, nothing follows at all — that is the undistributed middle, and it is the most frequent trap.
• A negative premise cannot produce an affirmative conclusion. That single rule eliminates a decoy in a large share of rounds.
• Watch for conclusions that claim more than the premises did. If a term is universal in the conclusion but not in its premise, the conclusion is illicit.
• Beware conclusions asserting that something exists. Premises about all of a category do not guarantee the category has any members.

Syllogica teaches formal logic and fallacy-spotting through hands-on region diagrams, making valid and invalid arguments visible.

• Skills: formal logic, syllogisms, logical fallacies, Venn diagrams
• Best for: roughly grades 8–12 (ages 13+)
• For parents & teachers: valid reasoning and common fallacies, made visual.

Two premises and a conclusion that either follows or does not is the syllogism, the form Aristotle set out in the Prior Analytics and the backbone of logic teaching for two thousand years.

The original design is in the wrong answers: each trap is broken in a specific, named way rather than being merely false.

That is what makes it teaching rather than testing. The classical syllogistic fallacies — undistributed middle, illicit major, affirming the consequent — were catalogued precisely because each one feels valid from the inside. A formal fallacy is an error of shape, not of fact, so naming the shape is the only reliable defence.

Syllogica is an original, free browser game that teaches formal logic and fallacy-spotting through hands-on region diagrams. It is built in-house and runs online.

A free, original browser game on PlayPendium. No download, no install.