My reading of Gal 5 is a conflict between the Holy Spirit and the flesh. I find no duality of nature in this passage.
Galatians 5:16
I say then: Walk in the Spirit, and you shall not fulfill the lust of the flesh.
there are four parties in this statement:
- the one speaking
- the one hearing
- the Spirit
- the flesh
since the one hearing is being encouraged to choose between the Spirit and the flesh, that person has in themselves both the will of the Spirit and the will of the flesh, and is able to follow either - otherwise what sense does it make to give such instruction at all?
if there was no desire in our flesh to do what is wrong, it would be completely unnecessary to encourage one another not to do those things.
what i see described both here and in Romans 6-8, and in other places, is a duality of substance that makes up our existence: a spiritual mind and a physical body.
before we were renewed in salvation in our minds, the two agreed with each other - in the unregenerate man, the mind is spiritually as dead as the flesh is.
now, in us our mind - which is spiritual - has tasted the Spirit of Life and is in disagreement with our body, and should bring that body into subjection.
Romans 8:23
we also who have the firstfruits of the Spirit, even we ourselves groan within ourselves, eagerly waiting for the adoption, the redemption of our body.
the body of flesh is not yet renewed, but it is still part of us. in the resurrection it will be changed, and cleansed, without sin, and there will be in us no more clash of will