A friend sent me this excellent article by Johnny D., entitled "Salvation and Separation". It's available on STEM Publishing: http://www.stempublishing.com/authors/darby/NOTESJOT/40010E.html.
Here's a small sample:
Before God, can you mend the first Adam? Will you educate him, and get any good out of him? You will not. God tried it, and it ended in the death of His Son. The very world we are living in is the world that had God in it, but it turned Him out. The flesh that I have got in me has had that Christ presented to it, and it rejected Him - morally, that is. We cannot now, of course, kill Him outwardly.
But people put this flesh under law, and they fancy they can school it. Do you think they would insist so upon law, if they were sure and certain that the only thing it can do is to damn them?
It's in Notes and Jottings, starting on page 46.