“Mending Wall” explores the line between the human and natural worlds. The wall is fundamentally shown to be an artificial object that imposes precariously on the natural landscape. The poem’s earliest lines show how the wall’s existence is tenuous, given the natural forces working against it, freezing and swelling the ground underneath the wall and scattering its stones. Later, when the speaker and his neighbor repair the wall, the very laws of physics seem to be working against their efforts. The men “use a spell” to make the stones balance, shouting “Stay where you are until our backs are turned!” Even the environment which the wall traverses belies its presence—indeed, the speaker remarks that the adjacent swathes of pine and apple trees have no need for an intervening border. It should be noted that there are human forces, too, that threaten the wall’s artificial existence, including “the work of hunters” and the speaker himself. But even in such instances, human destructiveness is framed in terms of the natural: as the speaker says, “Spring is the mischief in me.” 

Conversely, the neighbor’s efforts to repair the wall, which the speaker finds mysterious, are framed in terms that are unnatural: the neighbor “moves in darkness as it seems to me, / Not of woods only and the shade of trees.” Ultimately, the wall’s artifice lies in the way it apportions and simplifies the world. But the neighbor’s drive to uphold the wall is a desire to divide a natural world that knows no such divisions, and so the wall will remain embattled and provisional.