How do the characters contribute to the development of the central idea in Part A? The speaker worries over the effect of elves on the wall. His neighbor worries over the effect of hunters on the wall.

The speaker worries that his apple orchard will interfere with his neighbor's pine trees. His neighbor does not worry about apples falling from the orchard.

The speaker urges his neighbor to invest in cattle to support the wall. His neighbor wants a wall regardless of livestock.

The speaker believes that it is important to know what is being walled in or walled out. His neighbor believes that, regardless of the reason, good fences make good neighbors.