How to use:
- Choose a round length (10, 15, or 20 questions) and a difficulty, then click Start
- Each question shows premises and a conclusion. Treat the premises as absolutely true — even if they're unrealistic or use made-up categories
- Judge whether the argument is Valid (the conclusion must be true whenever the premises are) or Invalid (the conclusion could be false even with true premises)
- After each answer you get instant feedback naming the logical form — that's where the learning happens, so read it
- Questions are generated fresh each round, roughly half valid and half invalid, so you can't pattern-guess
What "valid" means (and doesn't):
- Validity is about structure only. "All cats are planets; all planets are loud; therefore all cats are loud" is perfectly valid — the premises are absurd, but IF they were true, the conclusion would have to be
- An argument with a true, sensible conclusion can still be invalid if the conclusion doesn't follow from the premises given
- The single most useful question to ask: "Can I imagine any situation where the premises hold but the conclusion fails?" If yes, it's invalid
Forms you'll practice:
- Standard: modus ponens and modus tollens (valid), affirming the consequent and denying the antecedent (the two classic invalid look-alikes), core syllogisms, converse errors, and comparison chains
- Advanced adds: hypothetical syllogism chains, disjunctive ("at least one is true") arguments, the undistributed middle, "some/not" conversion traps, and four-person comparison chains
Tips:
- For "if–then" arguments, find which part is affirmed or denied: affirming the "if" or denying the "then" is valid; the reverse two are invalid
- For category arguments, sketch circles in your head — if you can draw the premises with the conclusion false, it's invalid
- Made-up category names (Lorps, Mibs) are deliberate: they force you to judge structure, since there's no real-world knowledge to lean on
- A high score here transfers directly: these same forms appear in aptitude tests, law-exam logic sections, and everyday arguments dressed in persuasive language