This study has been undertaken on the assumption that when Paul spoke of principalities, authorities, powers, world-rulers, and elemental spirits, he was using mythological language to describe spiritual realities with which he and his fellow Christians had personal acquaintance. The first three chapters trace the history of three Jewish beliefs which contribute to Paul's theology: that God had set the pagan world under the authority of angelic governors, that the Law was given and guarded by angels, whose history strangely resembles that of Satan, and that the powers of nature are not entirely subservient to God's sovereignty. In each case the powers represent a divine authority corrupted by human sin. The last chapter attempts to show how Paul envisaged the cross as a victory over the powers.