I'm not able to move forward from step 4. I've tried Implication Introduction applied to 3 and 4 but nothing happens, any help is much appreciated.

enter image description here

  • 1
    I think you started in a good way. You can assume p(X) and use Implication Elimination to derive q(X).
    – F. Zer
    May 12, 2020 at 23:22

2 Answers 2


As F.Zer commented, before you can use Implication Introduction you must first make an assumption.

You must derive r(X) under the assumption of p(X), so that you may derive p(X) ⇒ r(X) by Implication Introduction.

  • Thanks a lot guys, I followed those steps and figured it out. I'm leaving the answer here just in case it helps anyone. May 13, 2020 at 13:25

enter image description here Final answer for this exercise is in the screenshot below.

You must log in to answer this question.

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