What Makes an Argument Valid · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Valid does not mean true

Personal & Social Development · Ethics & Philosophy · ages 16-18
Name ______________________   Date ____________

  1. What does valid mean for an argument?

    • The premises are all true
    • The conclusion is true
    • The conclusion must be true if the premises are true

  2. Mara says: since the cafe uses fresh beans, and fresh beans taste better, you will love our coffee. Which line is her conclusion?

    • The cafe uses fresh beans
    • Our coffee tastes better
    • Fresh beans taste better

  3. A valid argument always ends in a true conclusion.

    Circle one:   True   False

  4. Hastings was in 1066, tamaracks are conifers, therefore Paris is the capital of France. All true, yet the argument fails. What is wrong?

    • The premises do not support the conclusion
    • One of the premises is false
    • The conclusion is false

  5. All cats can fly. Mittens is a cat. So Mittens can fly. Why is this argument still valid?

    • If the premises were true, the ending would have to be true
    • Cats really can fly
    • Mittens is a famous cat

  6. What must you add to validity to get soundness?

    • A longer conclusion
    • True premises
    • More premises

  7. Which of these arguments is sound?

    • All mammals breathe. A whale is a mammal. So a whale breathes.
    • All birds can talk. A crow is a bird. So a crow can talk.
    • Fish live on land. A salmon is a fish. So a salmon lives on land.

  8. If it rains, the grass is wet. The grass is wet. So it rained. Is this valid?

    • Yes, since both lines are true
    • Yes, since wet grass proves rain
    • No, since a sprinkler could have wet the grass
LightMySky · lightmysky.comW1-mt_W72nTJmeOI-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Valid does not mean true W1-mt_W72nTJmeOI-s1

  1. The conclusion must be true if the premises are true · Validity is only about the link. True premises force a true conclusion, but validity never checks the premises.
  2. Our coffee tastes better · The conclusion is the claim the reasons point at. Both bean facts exist to support the coffee tasting better.
  3. False · False. A valid link fed by false premises can still land somewhere false, like Mittens the flying cat.
  4. The premises do not support the conclusion · Truth cannot rescue reasoning. These true lines give no path at all to the ending.
  5. If the premises were true, the ending would have to be true · Assume the start for a moment. A flying cat species plus Mittens the cat leaves no escape from the ending.
  6. True premises · Soundness is a valid link plus a true start. Either part alone falls short.
  7. All mammals breathe. A whale is a mammal. So a whale breathes. · Only the whale case pairs a tight link with a true start. The other two reason well from falsehoods.
  8. No, since a sprinkler could have wet the grass · This affirms the result and reasons backwards. Other causes give the same result, so the ending does not follow.
Worksheet · LightMySky