Four marks of a Christian are set forth in the Book of Galatians. First, a Christian is one who has the living Christ living in him. "I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me" (Gal. 2:20).
Second, a Christian is one who has the Holy Spirit within him, for in Galatians 4:6 we "And because ye are sons [if we are born again into His family], God sent forth the Spirit of his Son into your hearts." He is the One who really begets us, or creates us anew, and makes us believers. He also creates in us the new character from which Christian conduct comes. Christian conduct does not make a Christian, but a true Christian, one who is born of the Holy Spirit, will have Christian conduct as well.
In the third place, a Christian is one who has shared the cross experience with Christ as the basic solution of his personal problems. We all have come under this experience of the cross although we may not all have understood it. The key text on this subject is "I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me" (2:20). When Christ died, I died with Him, and when He arose, I arose with Him.
In the fourth place, the Christian is one who is possessed of a life that is so divine, so ideal, that it cannot be pushed into a mold of external regulations. We have a new life, a life from God, which is Christ Himself.
"Examine yourselves, whether ye be in the faith; prove your own selves" (2 Cor. 13:5).