Logic 2, Chapter 6, Day 3, No. 14, 5th item

[reimejo]

My daughter and I are stumped. The original enthymeme from No. 12 is:

If something doesn't cause crime, then it shouldn't be banned
And guns don't cause crime

The instructions for No. 14 indicate that for this problem contraposition is required on the major premise.

The answer key shows this as the major premise:

No thing which does not cause crime is a thing which should be banned

However, since contraposition involves conversion as one step, wouldn't we end up with "being banned" in the subject and "causing crime" in the predicate?

Would obversion alone suffice?

Hoping for help,
Jon

[martin]

Jon,

Sorry for the delay. This response is from Mr. Piland:

The missing premise should actually be "Guns should not be banned", or "No gun is a thing that should be banned." The full argument would be:

(1) All things that should be banned are things that cause crime
(2) No guns are things that cause crime
(3) No guns are things that should be banned

Contraposition can only be performed on A and O statements, so the major premise should originally be: All things that don't cause crime are things that should not be banned. Then contraposed it results in (1). Then, Guns don't cause crime = (2) No guns are things that cause crime, resulting in the conclusion (3) No guns are things that should be banned.

Thank you.