In "Holy Sonnet IV," the metaphysical poet John Donne generates a powerful tension as meaning and emotion strive within and against the metrical form of the Petrarchan sonnet.
Donne employs the interplay of form with emotion in this sonnet. Much like the other Holy Sonnets, the tone is one of fear and trepidation, which emanates from the poet's awareness of his sinfulness, a condition which causes him to doubt that his soul can be saved.
In the octave (rhyme scheme abbaabba), the speaker presents the problem of his soul's being black with sin: "Oh, my black soul!" He compares his soul to a pilgrim who has committed treason while abroad and, therefore, cannot return to his country. Or, his soul is like a thief who desires his release from prison until he is given a death sentence; then, he wishes for that imprisonment, as it is preferable to death. Clearly, there is a sense of despair in the soul's situation; this sense is underscored with the repetition of the first pattern of rhyme: abba.
Then, in the sestet (rhyme scheme cdcdee), the volta, which introduces a change in tone (marked by the change in rhyme scheme), presents at first a paradoxical dilemma: The speaker realizes his soul is in need of grace in order to repent. As the rhyme of the first two lines is repeated, the idea of grace reappears as the speaker realizes that his soul is so black with sin that it cannot receive this grace unless he repents:
Yet grace, if thou repent, thou canst not lacke;
But who shall give thee that grace to begin?
Faced with this spiritual dilemma, the poet realizes that only the intervention of Christ's dying on the cross -- "That being red, it dyes red soules to white" -- and its paradox of turning souls bloodied with sin to the white of redemption can save him. This solution of Christ's intervention appears in the rhyming final two lines, which change the rhyme scheme again.
In Sonnet IV Donne is aware of death coming in the form of illness. He rails at mankinds weakness and sinful nature and speaks of being lost to the joy of Heaven. He ends this sonnet by saying you can die as you are and be lost, or you can be washed in the blood of the Lamb (Jesus) which will turn you white again (pure, redeemed, forgiven) and spend eternity with the Lord.