The protagonist in Shakespeare's Macbeth reveals his self-divided psyche in a number of soliloquies and asides. The inner conflict in Macbeth is between good and evil, between the fair(conscience) and the foul(ambition), colaterally operative in him. Even Lady Macbeth becomes a victim of mental disorder because of the conflict between her natural feminine self and the assumed masculine cruelty. In Browning's dramatic monologue, Porphyria's Lover, the spaking persona is a guilt-stricken soul divided between his possessive love for the woman and his lurking fear to be dispossed of the same. The poem reads like a psycho-analytic confession of guilt of a person who chooses to kill his beloved only to perpetuate his love. Shakespeare's play is modelled on the Morality structure to dramatize the theme of self-damnation.
Both use the theme of Disturbed Minds to show what happens when a person is put under prolonged pressure. For Macbeth, this is the pressure to become king. For Porphyria's lover, it is pressure to keep going with a relationship they would rather be rid of.