This study interprets Jesus' parables and the sayings tradition regarding the Kingdom of God from a cognitive linguistic understanding of metaphor. It also shows what contribution the theory of metaphor can make when the parables and aphorisms are studied in research on the historical Jesus. The metaphoric nature and polyvalency of the parables and aphorisms of the Jesus tradition undermine their value for research on the historical Jesus. The author doubts whether the parables and sayings of the Jesus tradition can be employed to reconstruct the historical Jesus.