The narrator in "Mending Wall" is tellling about the annual work involved in rebuilding the rock wall that separates his apple orchard from the pines on his neighbor's property. As they labor, he questions why they must do this every spring. He understands the need for fences to keep cows in their pasture; however, he points out to his neighbor on the other side of the stone wall that "But here there are no cows" It seems to the narrator that there really isn't a good reason to maintain the separation.
The neighbor is uninterested in changing old patterns and understandings, is unwilling to open up to new possibilities and associations. He wants to continue on the basis of the relationship of separation that he has known all his life, handed down from his father.
He moves in darkness as it seems to me~
Not of woods only and the shade of trees.
He will not go behind his father's saying
The neighbor maintains the lesson learned from his parent, that it is important to keep one's own property enclosed and protected and that it is equally important to keep others' property out. This is accomplished by maintaining the structures that insure the separation. "Good fences make good neighbors."