Before I built a wall I’d ask to know What I was walling in or walling out, (lines 33-34)
The speaker wishes that his neighbor will simply ask questions and investigate. Perhaps, the speaker could care less about whether or not there is a wall, and he just hungers for some good ol’ debate.
Something there is that doesn’t love a wall, That wants it down.’ I could say ‘Elves’ to him, (lines 36-37)
When we hear this first line repeat towards the end of the poem, we realize that the speaker has not uncovered the mystery of the wall-destroyer. However, we also start to realize that the speaker’s focus shifts from the wall itself to his quiet neighbor.