The contraries that lie in Blake's work and in his theological and philosophical beliefs are most evident in the paradox of how printing is characterized as both corrosive ("melting apparent surfaces away") and as permanent through his etching method. This paradoxical nature of printing is also seen later in the same passage when Blake defines the duality of being as both "prolific and devouring" (plate 16).
For Blake, everything from printing to existence has a dual nature, one that is both unified and in opposition. Thus, there can be a "Marriage of Heaven and Hell."

In "The Clod and the Pebble," this polarity is seen in the exchange between the two objects about love. First, the two objects the poet chooses are in themselves representative of this unified opposition. The clod of clay is inconsistent, unfixed and can easily be washed away and "Trodden with the cattle's feet." This is much like the corrosive aspect of Blake's printing. Like the corrosives, the clay has a surface that can easily melt away by water or other elements. Similarly, the pebble represents the other polarity of printing because of its permanency, fixity and rigidity. Unlike the clod, the pebble does not melt away or fall apart; like the engraving methods of Blake, it is fixed. Also, the structure of the poem itself indicates this dual nature. There are three stanzas; the first and last stanzas virtually mirror each other, while the middle stanza in which the clod and the pebble are introduced, serves to unify the two arguments on love.

Though there is a contrast in the first and last stanzas, "a heaven in hell's despair" vs. "a hell in heaven's despite"; because one can be found in the other it implies a symbiotic relationship between the two- hence, a "marriage of heaven and hell."

It also seems absurd to have a clod of clay and a pebble discuss the nature of love. But since extreme polarities seem to be imbued in Blake's work, what better to discuss such a significant subject than that which is the most insignificant, a pebble and a piece of dirt?

Jinny Ahn