from Catholic Answers Jan/Feb 2004 V17#6 (the other one, from OSV edited by Fr Stravinskas, if I find it online I will post a link)
How to Read Sacred Scripture According to St. Augustine: A toure of De Doctrina Christiana, by Stephen Filippo
This article deals with the difference in relying on the literal or the figurative meaning of any word or passage in interpreting scripture, a really outstanding summary of Augustine’s teaching.
briefly: things which are clearly asserted in Sacred Scripture as instructions or rules governing life and belief, i.e. the Decalogue, are meant to be taken literally. Problems arise when the signs and language are ambiguous, or from interpreting literal signs as figurative and vice versa.
some ambiguous passages are made clear when referenced to other passages in scripture which offer clearer exegesis, some by referring to the original texts to interpret the meaning of the original writers, others by reference to Sacred Tradition and the rule of faith.
the first error is to take a figurative expression literally-only seeing the carnal sense of the passage and ignoring the spiritual reality (the pharisees reaction to Jesus’ healings on the Sabbath).
the second error is to take a literal expression figuratively. In general, he quotes from DDC III:x:14, understand as figurative anything in Holy Scripture which cannot in the literal sense be attributed to either an upright character or to a pure faith. so if the passage seems to be praising or promoting an action the person of good conscience knows to be objectively wrong, the passage is to be interpreted figuratively.
He then goes on to offer Augustine’s thesis in regard to judging sins and moral actions, by the current culture rather than by objective biblical moral teaching. In applying this to interpretation the saint says:
If the words of scripture contain harshness in apparent cruelty in the word or deed of God orhis saints, these words are efficacious in destroying the power of vice, and therefore are to be taken literally when scripture speaks plainly: against fornication, homosexuality etc.
Those things which appear wicked in word or deed, as applied to God or holy men (the prophets etc), are meant to be taken figuratively (the sacrifice of his son by Abraham for example.
He goes on if scripture is didactice in condemning vice or prescribing charity, it is literal, not figurative. If scripture appears to endorse vice or crime or condemn kindness, it is figurative. (i.e., cut off your right hand rather than sin with it).
Augustine often warns not to take a metaphor used in one passage as a universal meaning throughout: a lion represents Christ in one place (RV 5:5) and satan in another place (1Pet 5:8).
finally he warns with reference to OT not to apply universally today what was then accepted as a way of life (polygamy was permitted until God had brought the Jewish people through his progressive revelation to a more enlightened way).