The speaker asks his neighbor to help him mend the wall. It's something they do together every year. It seems that the speaker doesn't see any point in mending the wall, but his neighbor remains behind his old saying:
He only says, 'Good fences make good neighbors'.
Spring is the mischief in me, and I wonder
If I could put a notion in his head:
'Why do they make good neighbors? Isn't it
Where there are cows?
But here there are no cows.
Before I built a wall I'd ask to know
What I was walling in or walling out,
And to whom I was like to give offence.
Something there is that doesn't love a wall,
That wants it down.'
Yes, it looks like the speaker would want something more, or, at least, he would like to stop mending a wall which, from his point of view, serves no purpose.
The poem is a comment on isolation and being stuck with ideas that may have had some purpose in the past but no longer hold in the present. The speaker sees his neighbor as a "savage" who moves in "darkness," as someone who is ruled by outmoded thoughts and lack of originality. It should be noted, though, that most of my students, when we read the poem in class, side with the neighbor. They agree that "good fences make good neighbors."