Bishop Wright has some thoughtful comments in his: Paul for Everyone: Romans: Chapters 1-8. According to N.T. Wright, understanding what Paul’s definition of “flesh” is in Romans will help settle Paul’s distinction between “fleshly” and “spiritual.” He writes:
But what do ‘fleshly’ and ’spiritual’ mean? The first term, particularly, is so problematical that it would be nice (as I have tried to do with some other technical language) to avoid it altogether, but I have found that doing so produces even worse tangles. Better to learn, once and for all, that when Paul uses the word ‘flesh’ and other similar words he does not intend us simply to think of the ‘physical’ world, in our normal sense, as opposed to the ‘non-physical’. He has other language for that.
The word we translate, here and elsewhere, as ‘flesh’ refers to people or things who share the corruptibility and mortality of the world, and, often enough and certainly here, the rebellion of the world. ‘Flesh’ is a negative term. For Paul as a Jew the created order, the physical world, was good in itself. Only its wrong use, and its corruption and defacing, are bad. ‘Flesh’ highlights that wrong use, that corruption and decay. (p.140-41)
This is a helpful definition. What N.T. Wright has done is correct improper dichotomies in the text that are simply not found, but rather, take its roots in Platonic dualism. This is, furthermore, a stern rebuke of those who would like to use concepts such as “flesh” to identify everything that belongs to this world. In this worldview, the flesh can never be redeemed and the world is merely a necessary evil. The text simply will not allow these faulty ideas to occur. It has been the purpose of God to redeem the flesh and this world, hence, it is the corruption and defacing of the “flesh” that we as baptized Christians must avoid.