Definitions, as I have pointed out before, are different than Circumstances. For the sinner, it is of some moment and relief that Christianity changes the definition of a man rather than his circumstance. The rest of the world's religions (and much of Christendom) stress the religious circumstances of the life they recommend. The New Covenant has made a man's nature different. He is redefined. Whatever his circumstance, Jew or Gentile, male or female, slave or free, his definition has shifted and he is now filled with the Holy Spirit. This is necessary to even call yourself a Christian for "you are not in the flesh, you are in the Spirit, if in fact the Spirit of God dwells in you. Any one who does not have the Spirit of Christ does not belong to him." Romans 8:9
Many churches give a list of circumstances (from wet the baby to walk the aisle) perhaps because the circumstances of a Christian's life do change. You can't change the definition of something without it changing the world the new being inhabits. This will be so much that, as St. James says "I, by my works, will show you my faith." He didn't say "I will create my faith."
The worldly mind takes this continuum between who you are and what you do and switches where the definition resides. "I'll make a faith," says he, " from my ritual to moral to cultural deeds and it will be the biggest, grandest Christian faith you ever did see." He thinks that the definition is made by the circumstances not vice versa. He looks at the change described by the apostles and falls into the same slavery that he came out of.
If a man is defined as a featherless biped and believes wholeheartedly that that circumstance is what makes him a man, two errors are eventual. One, a plucked chicken is a man and, two, if he loses a leg, he lost his humanity.
Applied, we see that someone who insists that a Christian will be defined by x-ritual observance and by x-cultural condition, the church will soon (and has been) cumbered with those who meet the external definition who have not Christ and some who have Christ will be left wondering, should they lose access to x-ritual, if they are Christians.
The Christ says, "You must be born again."
Let Christ make a new man of you.
"whereas the aim of our charge is love that issues from a pure heart and a good conscience and sincere faith." I Timothy 1:5