[Edited: June 14, 2010]
A really interesting passage from Francis Turretin on, what we perhaps could call, a right use of the four-fold interpretation of Scripture (i.e. the quadriga).
“Distinguish the sense of the Scriptures from the application– the sense is only one, whether simple (in the histories, precepts and prophecies openly proposed) or composite (in the typical); whether proper (enunciated in proper words) or figurative (in figurative words). But the application can be diverse, both for instruction (didaskalian), reproof (elenchon), correction (epanorthosin), etc. which are the theoretical and practical uses of the Scriptures. Thus allegory, anagogy and tropology are not so much diverse senses as applications of one literal sense. Allegory and anagogy refer to instruction (didaskalian), but tropology to correction (epanorthosin)” (Turretin, Institutes, 2. XIX. VI.).
Turretin’s Institutes can be purchased here.