Romans 7:17-18 — Now then it is no more I that do it, but sin that dwelleth in me.
For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
Now = this being the case (not referring to time)
Do = practice, as in verse 15
no more = it can no longer be maintained as an argument
flesh (as in Romans 6:19) = human nature apart from divine influence
good (agathos — first usage in verse 18) = beneficial
good thing — even those things that seem good from a natural point of view are void of goodness without a right relationship with God
good (kalos — second usage in verse 18) = intrinsically good
Paul is saying that he is incapable of doing anything beneficial in his flesh that will produce real good.