The Bible and The Tempest

Is there a point of tension between the perspicuity of Scripture and the grammatico-historical method? To the extent that correct exegesis requires background information about the text, does that undercut the perspicuity of Scripture? A few points:

i) It's possible that the Protestant Reformers exaggerated the perspicuity of Scripture. That's not a fatal concession to Catholicism unless Catholicism is a viable alternative. Moreover, that just shifts the issue, since exegeting church fathers, papacy encyclicals, conciliar documents, Aquinas et al. raises the same need for background information. Catholic sources can't be interpreted in a historical vacuum. 

It's not as if popes, church fathers, and Scholastic theologians are more perspicuous than the Bible. Indeed, that adds 2000 years of additional layers to sift through. 

ii) The Protestant claim is not that Scripture is uniformly perspicuous. To say background information is sometimes necessary to exegete a particular passage doesn't imply that all of Scripture or most of Scripture is obscure without the illumination and clarification of background information. 

iii) Apropos (ii), it's possible both to overemphasize and underemphasize the necessity of background information. Let's take a comparison. To understand the language in The Tempest, it helps to have an annotated edition, like A. L. Rowse. But once you known the language, the basic plot and motives of the characters are comprehensible. Indeed, Shakespeare wrote it to make sense on its own terms, at the level of the story. 

But according to Renaissance historian Frances Yates, The Tempest is a political allegory. Cf. The Occult Philosophy of the Elizabethan Age (Routledge, 1979), based on court wizard John Dee. Suppose we grant that interpretation for the sake of argument. That would mean there's a whole hidden dimension to The Tempest. It moves on two levels. There's the overt story, and then there's a parallel story it alludes to. A story behind the story. If true, that would certainly fill in our interpretation of The Tempest. It would go two-levels deep. 

But even if that's true, it doesn't invalidate the overt meaning of the story. The overt meaning of the story is independent of the subtext, in the sense that it's a self-contained story with a dramatic logic all its own. It can stand alone without any reference to the underlying allegory. It enjoys a certain interpretive autonomy in that regard. The story is complete without the allegory. 

By comparison, even if the reader is missing the subtext of certain biblical passages, that doesn't ipso facto falsify a textual reading. Knowledge of the subtext may enrich the overall interpretation, but it doesn't necessarily correct a textual reading.