Objection 1. It would seem that it does not belong to the Sovereign Pontiff to draw up a symbol of faith. For a new edition of the symbol becomes necessary in order to explain the articles of faith, as stated above (Article 9). Now, in the Old Testament, the articles of faith were more and more explained as time went on, by reason of the truth of faith becoming clearer through greater nearness to Christ, as stated above (Article 7). Since then this reason ceased with the advent of the New Law, there is no need for the articles of faith to be more and more explicit. Therefore it does not seem to belong to the authority of the Sovereign Pontiff to draw up a new edition of the symbol.
Objection 2. Further, no man has the power to do what is forbidden under pain of anathema by the universal Church. Now it was forbidden under pain of anathema by the universal Church, to make a new edition of the symbol. For it is stated in the acts of the first council of Ephesus (P. ii, Act. 6) that "after the symbol of the Nicene council had been read through, the holy synod decreed that it was unlawful to utter, write or draw up any other creed, than that which was defined by the Fathers assembled at Nicaea together with the Holy Ghost," and this under pain of anathema. The same was repeated in the acts of the council of Chalcedon (P. ii, Act. 5). Therefore it seems that the Sovereign Pontiff has no authority to publish a new edition of the symbol.
Objection 3. Further, Athanasius was not the Sovereign Pontiff, but patriarch of Alexandria, and yet he published a symbol which is sung in the Church. Therefore it does not seem to belong to the Sovereign Pontiff any more than to other bishops, to publish a new edition of the symbol.
On the contrary, The symbol was drawn us by a general council. Now such a council cannot be convoked otherwise than by the authority of the Sovereign Pontiff, as stated in the Decretals [Dist. xvii, Can. 4,5. Therefore it belongs to the authority of the Sovereign Pontiff to draw up a symbol.
I answer that, As stated above (Objection 1), a new edition of the symbol becomes necessary in order to set aside the errors that may arise. Consequently to publish a new edition of the symbol belongs to that authority which is empowered to decide matters of faith finally, so that they may be held by all with unshaken faith. Now this belongs to the authority of the Sovereign Pontiff, "to whom the more important and more difficult questions that arise in the Church are referred," as stated in the Decretals [Dist. xvii, Can. 5. Hence our Lord said to Peter whom he made Sovereign Pontiff (Luke 22:32): "I have prayed for thee," Peter, "that thy faith fail not, and thou, being once converted, confirm thy brethren." The reason of this is that there should be but one faith of the whole Church, according to 1 Corinthians 1:10: "That you all speak the same thing, and that there be no schisms among you": and this could not be secured unless any question of faith that may arise be decided by him who presides over the whole Church, so that the whole Church may hold firmly to his decision. Consequently it belongs to the sole authority of the Sovereign Pontiff to publish a new edition of the symbol, as do all other matters which concern the whole Church, such as to convoke a general council and so forth.
Reply to Objection 1. The truth of faith is sufficiently explicit in the teaching of Christ and the apostles. But since, according to 2 Peter 3:16, some men are so evil-minded as to pervert the apostolic teaching and other doctrines and Scriptures to their own destruction, it was necessary as time went on to express the faith more explicitly against the errors which arose.
Reply to Objection 2. This prohibition and sentence of the council was intended for private individuals, who have no business to decide matters of faith: for this decision of the general council did not take away from a subsequent council the power of drawing up a new edition of the symbol, containing not indeed a new faith, but the same faith with greater explicitness. For every council has taken into account that a subsequent council would expound matters more fully than the preceding council, if this became necessary through some heresy arising. Consequently this belongs to the Sovereign Pontiff, by whose authority the council is convoked, and its decision confirmed.
Reply to Objection 3. Athanasius drew up a declaration of faith, not under the form of a symbol, but rather by way of an exposition of doctrine, as appears from his way of speaking. But since it contained briefly the whole truth of faith, it was accepted by the authority of the Sovereign Pontiff, so as to be considered as a rule of faith.
Source: Summa Theologica (New Advent)