I used the following example as a sound argument but was marked incorrect. I can't determine where I went wrong.

  1. All criminal actions are illegal
  2. All murder trials are criminal actions Therefore
  3. All murder trials are illegal
  • 2
    As Keelan said, that second premise is highly suspect. What you're doing there, whether knowingly or not, is abusing the ambiguity of the expression "criminal action", where in one context it's meant as "an action that is said to be 'criminal'" and in another as "an action that is part of a process for punishing criminal behavior". You get the idea. Commented Apr 28, 2015 at 6:45
  • Thank you for your help. I haven't learnt about ambiguity yet but can see how this has clouded the reasoning.
    – Trish
    Commented Apr 28, 2015 at 7:29
  • How would I go about re-wording the argument to remove the ambiguity?
    – Trish
    Commented Apr 29, 2015 at 12:04

1 Answer 1


A sound argument is an argument that is valid and of which all premises are true.

Your argument is valid, but the second premise is incorrect. A murder trial is not a criminal action. Maybe a murder is a criminal action - but that depends on the country you're in (to be on the safe side).

But, why don't you ask your teacher? :-)

  • Thanks. I seem to constantly trip up on this type of argument. I convince myself that the form is valid but then get lost with the premise truth values. My teacher isn't all that helpful unfortunately.
    – Trish
    Commented Apr 28, 2015 at 6:14
  • @Trish no problem, happy to help. Yep, a lot depends on the teacher... maybe this link can help you to understand the difference better: iep.utm.edu/val-snd - but it's tricky, I keep mixing them up as well.
    – user2953
    Commented Apr 28, 2015 at 6:15

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .