Read the excerpt from "Mending Wall." Spring is the mischief in me, and I wonder

If I could put a notion in his head:

“Why do they make good neighbours? 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.” I could say “Elves” to him,

But it’s not elves exactly, and I’d rather

He said it for himself.

What is the speaker’s mood in this excerpt?