I still think it's useful to recognize that the Bible was written in premodern language by premodern people. In fact, I suspect that we're liable to get ourselves into lots of trouble if we don't make this distinction when we interpret. But I'm still a little bit dubious about how the premodern/modern lens will actually affect how we read the text.
Because Randy's mentioned Ephesians 6, let's use that as our first example. Maybe it will help if we start by pretending that we've just picked up some Ancient text and started reading it.
Finally, be strong in the Lord and in his mighty power. Put on the full armor of God so that you can take your stand against the devil's schemes. For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.
OK, so the author starts talking about the devil and spiritual forces of evil, and immediately my brain starts sending up flares. "Danger!" it says. "Premodern language is being used here!" The author continues with his metaphor, recommending that his readers adopt defenses such as righteousness, truth, peace and faith against these supernatural attacks. Hugs, kisses, end of Ephesians, hooray.
Now how should I interpret this passage?
As a hair-splitting modern person, I think I should go about it by dividing the "truth" of the passage into two distinct parts. The first is the author's worldview, in which spiritual forces manipulate people and everyday events. The second is the author's statement, which is couched in the language of his worldview.
Now honestly, I'm very reluctant to try to evaluate the truth of a person's worldview. I can see some value to thinking of things in terms of spirits and spiritual realms, and it's not like empirical evidence can prove or disprove the existence of spirits. But the "spiritual realms" worldview is not my worldview. And so before I evaluate the point that the author is trying to make, I am obligated to translate it into language that is compatible with my worldview. In this case, I would be obligated to translate the author's supernatural language into something a little more helpful for my modern sensibilities; perhaps I would translate his "spiritual realms" language into a description of the shadowy regions of the human psyche.
As a result, I would then be able to get some benefit from the text: instead of trying to make myself believe that we are constantly manipulated by spirits, I can go ahead to what I think is the author's real point: that we should adopt virtues as means to produce goodness in ourselves, despite the ways in which we sometimes tend toward evil.
Put another way, I can treat the author's language about evil spirits as metaphor, and then try to apply or interpret the metaphor.
OK, great! So when I run into stuff about spirits manipulating the world, I'll just kind of gloss over that as a premodern metaphor, and try and translate the ideas into modern language.
God is spirit, and his worshipers must worship in spirit and in truth.
Thanks a lot, Apostle John. Now what am I supposed to do with that?