Spirit, Flesh, and Spiritual Schizophrenia

How often have we heard that, living within each believer, is a "good nature" and a "bad nature" which contantly vie for our allegiance? Sometimes the following illustration is used to bring the point home:

"The good part of us (the spirit) and the bad part of us (the flesh) are like two dogs in a fight. Which will win? Well, obviously the one we feed the most."

[Insert warning against secular music here.]

This principle certainly makes sense on the canine level, but is it Pauline? Is it really the case that we each have an angel on one shoulder and a devil on the other? And further, is the NIV's rendering legitimate, which translates sarx (flesh) as "sinful nature"?

I'll elaborate in future posts, but for now I'll just state my position: Neither the battle within the "wretched man" of Romans 7 nor the warfare between the "Spirit" and the "flesh" in Galatians 5 has anything to do with an internal struggle within the believer. The former is indeed an existential struggle, but not one that New Covenant saints need concern themselves with (see my post on Postmortem Remarriage below). The latter, Galatians 5, is a struggle in which believers engage, but the warring categories (flesh and Spirit) are not internal but external, not micro but macro, not individual but eschatological.

To live under a two-dogs-fighting paradigm for sanctification betrays a woefully under-realized eschatology. If we accept this as normative for the Christian life, we may as well put a bumper sticker on our car that reads, "Christians Aren't Perfect, Just Forgiven."

Thoughts?