A Christian is a man or woman who has been begotten by God to a new kind of life. When someone is begotten of God, there comes into his life a change so radical that the only thing that can be said is that life has begun all over again for him. In His dwelling place, there's regeneration. This is called the new birth, and it happens by the will and by the purpose of God (John 1:13). It is not something that a man achieves by his physical birth. This is the work of the Holy Spirit of God.