Presuppositions in exegesis

This nicely illustrates the decisive role of presuppositions in Biblical exegesis, as well as the value and the limitations of background data:

Swete acknowledges the relevance of R. H. Charles's research with Jewish apocalyptic texts when interpreting Revelation. Yet, Swete does not want to say that the key to understanding Revelation can be found among those earlier apocalyptic texts. Instead,  at most, Swete concedes that these additional texts help the exegete understand the stock images and symbols that were common among the persecuted followers of God at the end of the first century. Even then, however, Swete argues that these apocalyptic "phrases and imagery" belong "to the scenery of the book rather than the essence of the revelation." 

Most importantly, Swete, against the majority of NT scholars in his day, charted a new direction when he attempted to read the book of Revelation as a literary unity rather than a composite text that was pieced together from various sources In part because he believed the author received the entire message from God by direct revelation, Swete perceived a unified structure of visions in Revelation that fit neatly together…Swete did not want to say that John depended on these texts as sources or that John modeled the book of Revelation after these generically similar texts. A. Arterbury, "Swete, Henry Barclay," D. McKim, ed. Dictionary of Major Biblical Interpreters (IVP 2007), 958-59.