For about half of the entire history of the Church, it was common for a newly elected pope to retain his baptismal name. The first pope to take a different name was John II (533-35). He did so because his birth name was that of a pagan God, Mercury.

In two instances newly elected popes who had been baptized as Peter also changed their names, out of respect for the Apostle Peter whose successor they would be. They were John XIV (983-84) and Sergius IV (1009-12).

By the 16th century, however, the custom of retaining one's baptismal name had ended completely. The last pope to keep his birth name was Marcellus II, who died of a stroke less than a month after his election on April 9, 1555. Earlier in the same century, Hadrian IV, who was the last non-Italian pope until John Paul II was elected in 1978, had also retained his baptismal name.

The current pope, Benedict XVI, was baptized Joseph. Were it still the custom for a newly elected pope to retain his baptismal name, Joseph Ratzinger would be Pope Joseph I.

In fact, we have never had a Pope Joseph in more than 20 centuries of papal history. Given the popularity of the saint and his status as patron of the universal Church, it is remarkable that no pope has ever taken his name.

Joseph's feast day is one of the most important on the Church's liturgical calendar --- so important that it has been transferred this year from its usual place on the 19th of March to the 15th because of a conflict with Holy Week.

What do we actually know about St. Joseph? Less certainly than we know about St. Peter, even though Joseph's relationship with Jesus was much more intimate and long-standing than Peter's.

Joseph is mentioned as the father of Jesus in John 1:45 and 6:42, in Luke 4:22 and in Luke's genealogy of Jesus (Luke 3:23). He appears also in the infancy narratives (Matthew 1-2; Luke 1-2), where he is said to be of Davidic descent (Matthew 1:2-16, 20; Luke 1:27; 3:23-38).

Joseph was a carpenter by trade (Matthew 13:55) and trained his son as a carpenter as well (Mark 6:3).

Mary was betrothed, or engaged, to Joseph, but was already pregnant with Jesus before Joseph took her into his house. The Hebrew Scriptures (Deuteronomy 22:20-21) provided a harsh penalty (death by stoning) for the infidelity of a betrothed woman.

At first, Joseph, being a "righteous" or "just" man, chose to divorce Mary "quietly" to protect her from shame. But, according to the New Testament, an angel appeared to Joseph in a dream and instructed him to take Mary into his home, and informed him that the child had been conceived by the Holy Spirit and that his name would be Jesus (Matthew 1:20-21).

In a later dream, after the birth of Jesus, Joseph was told to take Mary and his son to Egypt and to remain there until Herod's slaughter of newborns had come to an end with Herod's own death (Matthew 2: 13-15).

Joseph, however, disappears from the New Testament after the family's pilgrimage to Jerusalem (Luke 2:42-52). He probably died sometime before Jesus began his public ministry.

Because of the biographical gaps, a number of apocryphal writings attempted to fill in the blanks. The Protoevangelium, or Infancy Gospel, of James claimed that Joseph was already an aged widower with children when he married Mary. How else to explain the many references to Jesus' brothers and sisters in Mark 3:31; 6:3; Matthew 12:46; 13:55; Luke 8:19; John 7:3-5; 1 Corinthians 9:5; and Galatians 1:19?

New Testament scholar Jerome Neyrey, S.J., however, discounts the various traditional explanations. The evidence for "stepbrother," he writes, is "merely legendary" (referring again to the Infancy Gospel of James 9:2 and 17:1).

On the other hand, the linguistic evidence for "brother" meaning "cousin" is "very thin." We have but one example in the whole Old Testament where a cousin might be called a "brother" (1 Chronicles 23:22). [See Father Neyrey's "brothers of Jesus," The HarperCollins Encyclopedia of Catholicism, pp. 198-99.]

The earliest evidence for a cult of Joseph in the West is not until the ninth century, in Irish martyrologies. Devotion to Joseph was later popularized by such prominent saints as Teresa of Avila, Francis de Sales and Ignatius Loyola.

Many religious congregations, hospitals and churches are dedicated to Joseph, and his name has been exceedingly popular for baptisms and confirmations.

Pius IX declared Joseph patron of the universal Church in 1870, and John XXIII added his name to the Canon of the Mass in 1962.

But still no Pope Joseph.

Fr. Richard McBrien is the Crowley-O'Brien Professor of Theology at the University of Notre Dame.