What the presence of Christ within means

^9-11 But you are not carnal but spiritual if the Spirit of God finds a home within you. You cannot, indeed, be a Christian at all unless you have something of his Spirit in you. Now if Christ does live within you his presence means that your sinful nature is dead, but your spirit becomes alive because of the righteousness he brings with him. I said that our nature is “dead” in the presence of Christ, and so it is, because of its sin. Nevertheless once the Spirit of him who raised Jesus from the dead lives within you he will, by that same Spirit, bring to your whole being new strength and vitality.

^12-13 So then, my brothers, you can see that we have no particular reason to feel grateful to our sensual nature, or to live life on the level of the instincts. Indeed that way of living leads to certain spiritual death. But if on the other hand you cut the nerve of your instinctive actions by obeying the Spirit, you are on the way to real living.