1. (∀x)(Px ⊃ Qx)
2. ∼(∃x)[(Px • Rx) • Qx]
3. (∃x)Rx / ∼(∀x)Px
-Which of the following propositions isnot a likely last line of the indented sequence for an indirect proof of the given argument?
A) Rd • ∼Rd
B) (∃x)(Px • Rx) • ∼(∃x)(Px • Rx)
C) Qd • ∼Qd
D) (∀x)(Px • Rx) • ∼(∀x)(Px • Rx)
E) Pd • ∼Pd

Question

Quizplus · Accepted Answer

Option B is not a likely last line of an indirect proof for the given argument because it directly contradicts the premise 2, which states that there does not exist an x such that Px and Rx and Qx are all true. An indirect proof typically aims to show a contradiction arises from assuming the negation of what you're trying to prove, but option B does not align with proving the conclusion ∼(∀x)Px from the given premises.

1. (∀X)(Px ⊃ Qx)