First, you can say that we believe that the bread and wine at Mass become the body and blood of Christ. Then add your own experience of encountering Real Presence, because, frankly, theological terms never get to the heart of the matter. No one comes to Jesus by means of a word like this.

Why do we have this word? Medieval theologians sought to explain why our eyes see bread and wine, yet we claim Christ truly present. Peter Lombard described how the physical elements are transformed and only the “appearance” of bread and wine remain.

During the Protestant Reformation, Eucharist was hotly contested. Most Reformers viewed Eucharist as a memorial meal. In response, the Council of Trent defended an actual substantial change—transubstantiation—using Lombard’s interpretation. In other words: best not to define a mystery precisely, but allow God to work.

Twentieth-century theologians introduced two more words to the conversation. Transignification emphasizes changes in meanings rather than in form. Bread and wine normally mean nourishment. Consecrated bread and wine signify nourishment with Christ's life.

Transfinalization focuses on ultimate purpose or “finality.” Food and drink for the body gain a new goal as food for the spirit. Still, the most vital change remains what happens to us who receive it.

Scripture
• Matthew 26:26-29; Mark 14:22-25; Luke 22:14-20; John 6:22-59; 1 Corinthians 11:23-26

Online
• Mysterium Fidei, Encyclical of Pope Paul VI on the Holy Eucharist
• World Council of Churches, Unity: The Church and Its Mission, with links to documents including Baptism, Eucharist, and Ministry
• "Why do Christians believe Jesus is God incarnate?" by Alice Camille

Books
• 101 Questions & Answers on the Eucharist by Giles Dimock, O.P. (Paulist Press, 2006)
• The Eucharist: A Mystery of Faith, by Joseph M. Champlain (Paulist Press, 2005)
• The Eucharist and the Hunger of the World by Monika K. Hellwig (Paulist Press, 1976)

The Twelve are listed in Mark, Matthew, Luke and Acts. Luke's two books show the most enthusiasm for this group, using "Twelve" frequently and interchangeably with "apostles." John refers to the Twelve only twice and never lists them.

The listings betray a hierarchy. Four names top every list: brothers Simon Peter and Andrew, and Zebedee’s sons James and John. Peter is always first. The other three vary. The next grouping is shuffled but consistent: Philip, Bartholomew, Matthew, and Thomas. The surprise is Bartholomew, who never speaks and of whom nothing is known.

The final four are James, son of Alphaeus; a disciple known as Thaddeus or Judas, son of James; Simon the Zealot, and Judas Iscariot, closing every listing as the least esteemed.

With two Simons, two James, and possibly three Judases, epithets or nicknames are added. Simon Peter is distinguished from the Zealot. Zebedee’s James is “the Greater,” and Alphaeus’ son “the Lesser.”  Thaddeus/Judas, assuming the same position on various lists, is shortened to Jude to lose the reviled name. Thomas is called “Judas, not the Iscariot” in John’s gospel and other extra-biblical texts. That identification is simply dropped.

In John's gospel, Andrew, Peter, Philip, and Nathanael are the original recruits. Nathanael? Since Philip recruits Nathanael, and Philip is paired with Bartholomew elsewhere, the idea that Nathanael IS Bartholomew is suggested. John gives Zebedee’s sons only a vague post-resurrection nod. John favors other followers: Sanhedrin member Nicodemus; Mary, Martha, and Lazarus of Bethany; Mary Magdalene, Joseph of Arimathea, and an unnamed “beloved” disciple. Thomas plays a heftier role, as does Judas. After Easter, Luke says, Matthias replaces Judas. The symbolic authority of Twelve lasts for a generation. As each is martyred, none are replaced.

Scriptures: Mark 3:14-19; Matthew 10:1-4; Luke 6:12-16; John 1:37-51; 3:1-15; 6:70-71; 11:16; 13:23; 18:15-16; 14:22; 19:26-27, 38-42; 20:1-29; 21:1-2, 7, 20-25; Acts 1:13

Books: 
Apostle: Travels Among the Tombs of the Twelve – Tom Bissell (New York: Vintage Press, 2017)Didache: The Teaching of the Twelve Apostles – Clayton N. Jefford (Salem, OR: Polebridge Press, 2013)