 As such, "A Poison Tree" appears to play-off the Christian idea of self-denial, and it is possible that Blake is relying on Emanuel Swedenborg's theme of piety concealing malice, which ultimately alienates the individual from their true identity and evil no longer appears to be evil.Blake's poem differs from Swedenborg's theory by containing an uncontrollable progression through actions that lead to the conclusion.The final murder is beyond the control of the narrator, and the poem reflects this by switching from past to the present tense.