A method of interpretation or exposition where the words contain a secondary meaning, other than the straightforward one. John Bunyan's Pilgrim's Progress is an allegory. In the OT, Isa. (5: 1–6) has an allegory of the vine. In Gal. 4: 24 Paul uses the account in Gen. 16 and 17 of Abraham's two sons in support of the opinion (which he already held) that Isaac, the son of a free woman, Sarah, represented the spiritual descendants of Abraham, whereas Ishmael, the son of a bond woman, Hagar, stands for those whose relation to Abraham is the inferior relationship of natural descent.
He means that the Genesis text bears a meaning over and above the literal, historical, meaning: Isaac stands for Christians, who came into a relationship with God as free sons. They have a faith like Abraham's: Isaac was born ‘through promise’. Hagar bore children with the status of slaves—meaning Jews in bondage to the Law. The two women of Genesis are identified by Paul with two different covenants—the old and the new—and with two different Jerusalems—one present and another above, heavenly. Paul quotes Isa. 54: 1 in Gal. 4: 27 about Jerusalem as it was before and after the Exile in Babylon: Sarah, who suffered the ordeal of being barren, will have more reason to rejoice than she who had a husband (Hagar). New Jerusalem, through the Church, offers so much more than the old: freedom, instead of slavery, the gospel instead of the Law.
At Alexandria Philo used the allegorical method in order to diminish references and notions in the OT which would be offensive to pagans, and Origen in Alexandria (c. 200 CE) continued the method in the interests of Christianity. Beneath uncongenial details of ritual and history, Origen found timeless truths. By suggesting that the OT had layers of meaning beyond the literal, he made it acceptable and affirmed the unity of both OT and NT, against such as Marcion.
Within the gospels, some of the parables are already given an allegorical interpretation in which the details of the parable are said to contain a deeper meaning, as with the Sower (Mark 4: 3–8, explained by 4: 14–20). For those who incline to a rigorous view that Jesus' parables had invariably only a single meaning, such allegorizing is evidence of a development within the community after the time of Jesus. This is not necessarily illegitimate: it is open to readers of different cultures and generations to give their own interpretations of the texts. The original author does not enjoy a kind of copyright of interpretation. He does but send it on its way, and it then acquires new meanings, though not fanciful or arbitrary ones. However, many scholars today accept that Jesus himself probably used some allegory in his parables.
Taking Paul's distinction (2 Cor. 3: 6) between ‘the letter and the spirit’, Christians interpreted in an allegorical way those provisions in the Law which they no longer observed, such as the whole system of ritual purity; by this means they both respected the authorship of their received scriptures (the OT) and also made them relevant to their own faith and practice. Christian Fathers after Origen were fond of the allegorical method and applied it to the NT: Augustine regarded all the details in the parable of the Good Samaritan as having ‘deeper’ meanings; thus, the inn (Luke 10: 34) which provided succour designates the Church.