Editing Pope Callixtus III (section)

==Early church career==
Borgia studied grammar, logic and the arts in Valencia and went in 1392 to the [[University of Lleida]] where he obtained a [[doctorate]] in both [[canon law]] and [[Civil law (legal system)|civil law]]. His early career was spent as a professor of [[law]] at the University of Lleida. Around 1411, he attended a sermon by [[Vincent Ferrer]]. Afterward, the [[Order of Preachers|Dominican]] said to the future pope: "My son, you one day will be called to be the ornament of your house and of your country. You will be invested with the highest dignity that can fall to the lot of man. After my death, I shall be the object of your special honour. Endeavor to persevere in a life of virtue."<ref>Rolfe, pp. 12–13</ref> Later, as pope, Borgia [[canonized]] Ferrer on 3 June 1455.<ref>{{cite book|last=Reinhart|first=Albert|url=http://www.newadvent.org/cathen/15437a.htm|title=St. Vincent Ferrer.|work=The Catholic Encyclopedia|volume=15|year=1912|publisher=New York: Robert Appleton Company}}</ref>

Borgia was chosen as a delegate of the [[Diocese of Lerida]] to the [[Council of Constance]] in 1416, but did not partake in the proceedings as King [[Alfonso V of Aragon]] was opposed to the council. Because of this he went to Barcelona as a representative of his diocese in a synod. Borgia cared strongly for the reestablishment of the unity of the church and his influence with the Aragonese monarch was the factor that allowed for the conclusion of the accord between the king and the new pope.

In 1418, he was named as the rector of San Nicolas of Valencia. He was also the vice-chancellor of the University of Lleida from 1420 to 1423. In 1424, he resigned his position and dedicated his service to the Aragonese king. In 1424, he was named as the apostolic administrator of the see of Mallorca. It was at that time that the king desired that he be made a [[Cardinal (Catholicism)|cardinal]]; [[Pope Martin V]] refused the request. During the [[Great Western Schism]] he supported [[Antipope Benedict XIII]] and was also the driving force behind [[Antipope Clement VIII]]'s submission to [[Pope Martin V]] in 1429.<ref>McBrien, p. 260</ref> He then served as a diplomat to the kings of [[Aragon]], especially during the [[Council of Basel]] (1431–1439).