In some Christian circles the idea of the Christian having two natures, is held as fact. And although the most popular translation among evangelicals, and my own preferred translation, the New International Version in its 2011 revision changed the translation of sarx from “sinful nature” to “flesh” in those passages in Paul which refer to the human propensity to sin, it still retained “sinful nature” in the two instances of sarx in Romans 7. It seems arguably to me, that “sinful nature” should have been scrapped altogether.
It seems that strictly speaking, the problem is indwelling sin, not the flesh itself. The problem with the flesh is that it is unable in and of itself to resist sin. And that’s because the flesh by itself was never meant to overcome sin. Humans are meant to be in union with God, so that the flesh overcomes sin by the Spirit from the Father through the Son.
This is a big study, debated among theologians, and certainly not resolved in a post like this. A study of Romans 7 and 8 is especially key in trying to come to some conclusion in this. As for me, I think the weakness of the flesh is completely due to the lack of human dependence on the Spirit through Christ’s death and resurrection. But maybe the flesh in itself is sinful, indwellling sin corrupting it, which is why one must make no allowance for its lusts. Whatever the case, I’m glad for the change the NIV did make.