hello Jimmy,
In a way the Church has defined who is within the bosom of the Church by defining who is not within the bosom of the Church. Anyone anathematized by Church leaders is cut off from the body of the Church and put outside the Church by the power of the Keys to the Kingdom which Jesus left with St. Peter. It would be my guess that the main reason for the Church to go to such great lengths to define “no salvation outside the Church” is to back up their power and authority of disipline in the Church through anathema.
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Throwing Stones
AnathemaIn passing this sentence, the pontiff is vested in
amice, stole, and a violet cope, wearing his mitre, and assisted by twelve priests clad in their
surplices and holding lighted candles. He takes his seat in front of the altar or in some other suitable place, amid pronounces the formula of anathema which ends with these words: “Wherefore in the name of
God the All-powerful, Father, Son, and Holy Ghost, of the Blessed Peter, Prince of the Apostles, and of all the saints,
in virtue of the power which has been given us of binding and loosing in Heaven and on earth, we deprive N-- himself and all his accomplices and all his abettors of the
Communion of the Body and Blood of Our Lord, we separate him from the society of all
Christians,
we exclude him from the bosom of our Holy Mother the Church in Heaven and on earth, we declare him
excommunicated and anathematized and
we judge him condemned to eternal fire with Satan and his angels and all the reprobate, so long as he will not burst the fetters of the demon, do penance and satisfy the Church; we deliver him to
Satan to mortify his body, that his soul may be saved on the day of judgment.” Whereupon all the assistants respond: “Fiat, fiat, fiat.” The pontiff and the twelve priests then cast to the ground the lighted candles they have been carrying, and notice is sent in writing to the priests and neighbouring bishops of the name of the one who has been
excommunicated and the cause of his
excommunication, in order that they may have no communication with him. Although he is delivered to
Satan and his
angels, he can still, and is even bound to repent. The Pontifical gives the form for absolving him and reconciling him with the Church. The
promulgation of the anathema with such solemnity is well calculated to strike terror to the criminal and bring him to a state of repentance, especially if the Church adds to it the ceremony of the Maranatha.
Quoted from New Advent Catholic Encyclopedia
newadvent.org/cathen/01455e.htm