"But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if anyone does not have the Spirit of Christ, he is not His." Romans 8.9
Being in the flesh is to be a prisoner of the heart, to cater to the lusts of the soul and feelings.
Being in the Spirit is to live in the spiritual world, the world of certainty, the conviction and of supernatural faith.
If anyone confesses Jesus as Lord but does not live by faith, he has nothing to do with him.