How does Robert Frost use ambiguity to present his message about walls and neighbors in the poem "Mending Wall"? What evidence supports the idea...

Robert Frost's poem “Mending Wall” gives the reader the initial impression that the wall in question is a good thing, but it doesn't take long to see that the speaker does not really care for the wall at all.

The poem's ambiguity lies in the fact that we cannot really be certain if we need walls at all—do they help us or hurt us? Frost hints at the fact that it depends on the type of wall we are talking about.

The title implies that the wall needs work, or “mending.” The reader immediately assumes that if the wall needs to be mended then it must be important. Why would we bother to fix something that we didn't need in the first place? But, in the poem's first line, Frost brings that assumption into question:

Something there is that doesn’t love a wall,

He reverses the usual word order a bit with “Something there is” (instead of “There is something”) for reasons that probably only he could tell you. But the line immediately changes our feeling about the wall, and we may be surprised at this quick thematic turn. The rest of poem essentially questions the need for this wall, or for any walls, for that matter.

Frost makes his most important point when he says:

Before I built a wall I’d ask to know What I was walling in or walling out

The only defense for the wall comes from the speaker's neighbor:

He only says, 'Good fences make good neighbors.'

By prefacing the remark with “He only says” Frost is showing a little obstinacy on the part of the neighbor—he won't listen to the speaker's questions about the wall.

Finally, in the poem's final three lines, the neighbor repeats himself:

He will not go behind his father’s saying, And he likes having thought of it so well He says again, ‘Good fences make good neighbors.'

The line, “He will not go behind his father's saying” suggests that our desire for walls has gone unexamined through the ages—we merely accept the tradition of walling our stuff in and our neighbors out.