In this section of "An Essay on Criticism" Alexander Pope is expanding on his notion of the relationship of art to nature, as both having underlying structure that creates harmony out of apparent diversity or chaos. Pope was a Roman Catholic who believed that the underlying order of the world was evidence of its divine nature, and thus whatever superficial chaos we see in disordered nature, e.g. a boulder strewn plain, the apparently random pattern of hills, even floods and storms, still are outward manifestations of a Creation ordered by a divine will, just as the poet makes order out of words. This in both nature and literature:
Where order in variety we see,
And where, though all things differ, all agree.