What type of source is the Profession of Faith issued by the Council of Trent, 1545-63?

On 15 March 1517, the Fifth Council of the Lateran closed its activities with a number of reform proposals (on the selection of bishops, taxation, censorship and preaching) but not on the major problems that confronted the Church in Germany and other parts of Europe. A few months later, on 31 October 1517, Martin Luther issued his 95 Theses in Wittenberg.

A general, free council in Germany

Luther's position on ecumenical councils shifted over time, but in 1520 he appealed to the German princes to oppose the papal Church, if necessary with a council in Germany, open and free of the Papacy. After the Pope condemned in Exsurge Domine fifty-two of Luther's theses as heresy, German opinion considered a council the best method to reconcile existing differences. German Catholics, diminished in number, hoped for a council to clarify matters.

It took a generation for the council to materialise, partly because of papal reluctance, given that a Lutheran demand was the exclusion of the papacy from the Council, and partly because of ongoing political rivalries between France and Germany and the Turkish dangers in the Mediterranean. Under Pope Clement VII (1523-34), troops of the Catholic Holy Roman Emperor Charles V sacked Papal Rome in 1527, "raping, killing, burning, stealing, the like had not been seen since the Vandals". Saint Peter's Basilica and the Sistine Chapel were used for horses. This, together with the Pontiff's ambivalence between France and Germany, led to his hesitation.

Charles V strongly favoured a council, but needed the support of King Francis I of France, who attacked him militarily. Francis I generally opposed a general council due to partial support of the Protestant cause within France, and in 1533 he further complicated matters when suggesting a general council to include both Catholic and Protestant rulers of Europe that would devise a compromise between the two theological systems. This proposal met the opposition of the Pope for it gave recognition to Protestants and also elevated the secular Princes of Europe above the clergy on church matters. Faced with a Turkish attack, Charles held the support of the Protestant German rulers, all of whom delayed the opening of the Council of Trent.