Catholicism is a broad term for the body of the Catholic faith, its theologies and doctrines, its liturgical, ethical, spiritual, and behavioral characteristics, as well as a religious people as a whole.

For many the term usually refers to Christians and churches, western and eastern, in full communion with the Holy See, known alternatively as the Catholic Church or as the Roman Catholic Church. However, many others use the term to refer to other churches with historical continuity from the first millennium.

In the sense of indicating historical continuity of faith and practice, the term "catholicism" is at times employed to mark a contrast to Protestantism, which tends to look solely to the Bible as interpreted on the principles of the 16th-century Protestant Reformation as its ultimate standard. It was thus used by the Oxford Movement.

According to Richard McBrien, Catholicism is distinguished from other forms of Christianity in its particular understanding and commitment to tradition, the sacraments, the mediation between God, communion, and the See of Rome. According to Orthodox leaders like Bishop Kallistos Ware, the Orthodox Church has these things as well, though the primacy of the See of Rome is only honorific, showing non-jurisdictional respect for the Bishop of Rome as the "first among equals" and "Patriarch of the West". Catholicism, according to McBrien's paradigm, includes a monastic life, religious institutes, a religious appreciation of the arts, a communal understanding of sin and redemption, and missionary activity.

Peter John Kreeft (born 1937) is a professor of philosophy at Boston College and The King's College. He is the author of numerous books as well as a popular writer of Christian philosophy, theology and apologetics. He also formulated, together with Ronald K. Tacelli, SJ, "Twenty Arguments for the Existence of God".

Kreeft took his A.B. at Calvin College (1959), and an M.A. at Fordham University (1961). In the same university he completed his doctoral studies in 1965. He briefly did post graduate studies at Yale University.

Kreeft has received several honors for achievements in philosophical reasoning. They include the following: Woodrow Wilson, Yale-Sterling Fellowship, Newman Alumni Scholarship, Danforth Asian Religions Fellowship, and Weathersfield Homeland Foundation Fellowship.

He joined the Philosophy faculty of the Department of Philosophy of Boston College in 1965. His intellectual reputation stems from his strengths in debating and summarizing the philosophical arguments of the major Western philosophers. He has debated several academics in issues related to God's existence. Shortly after he began teaching at Boston College he was challenged to a debate on the existence of God between himself and Paul Breines, an atheist history professor, which was attended by a majority of undergraduate students. Kreeft later used many of the arguments in this debate to create the Handbook of Christian Apologetics with then undergraduate student Ronald K. Tacelli, S.J..

Frederick Antony Ravi Kumar Zacharias (born 1946) is an Indian-born, Canadian-American evangelical Christian apologist. Zacharias is the author of numerous Christian books, including Gold Medallion Book Award winner Can Man Live Without God? and bestsellers Light in the Shadow of Jihad and The Grand Weaver. He is the founder and chairman of the board of Ravi Zacharias International Ministries, host of the radio programs Let My People Think and Just Thinking, and visiting professor at Wycliffe Hall of Oxford, where he teaches apologetics and evangelism. Zacharias studied as a visiting scholar at Cambridge University and held the chair in Evangelism and Contemporary Thought at Alliance Theological Seminary from 1981 to 1984. Commentator Chuck Colson referred to Zacharias as "the great apologist of our time."

Zacharias was born in Madras, India. Zacharias claims descent from a woman (of the Nambudiri Brahmin caste) and a low caste Boatman. Missionaries spoke to one of his ancestors about Christianity and thereafter the family was converted. Zacharias grew up in a nominal Anglican household, and he himself was an atheist until the age of 17, when he unsuccessfully tried to commit suicide by swallowing poison. While in the hospital, a local Christian worker brought him a Bible and instructed his mother to read to him out of John 14. Zacharias says that it was John 14:19 that touched him and caused him to commit his life to Christ.

Fr. Mitchell "Mitch" Pacwa ,(born 1949) S.J., is a Jesuit priest. He is bi-ritual, meaning that he can celebrate liturgy in both the Roman and Maronite rites. He is President and Founder of Ignatius Productions. He has taught at the University of Dallas and Loyola University Chicago and is now the Senior Fellow of the St. Paul Center for Biblical Theology.

Fr. Pacwa's father was opposed to his becoming a priest and especially against his becoming a Jesuit. Fr. Pacwa's father threatened to write him out of his will if he became a priest and did so on the day Fr. Pacwa celebrated his first Mass.

Fr. Pacwa earned his Ph.D. in Old Testament from Vanderbilt University. He also holds a Master of Divinity and S.T.B. from the Jesuit School of Theology at Loyola University. He is an accomplished linguist speaking several ancient languages, including Latin, Koine Greek, Hebrew, Aramaic, and Ugaritic, as well as the modern languages of German, Spanish, Polish, Hebrew, Arabic, French, and Italian.

Fr. Pacwa has mostly earned fame by being host of many TV shows. He gave the 2008 commencement address at the Augustine Institute in Denver.

Matthew Kelly (born David Allan Kelly, 9 May 1950, Urmston, Lancashire, England) is an English television presenter and Olivier-award winning actor. Having been trained as a theatre actor, he first came to public prominence as a television presenter of ITV light entertainment shows such as You Bet! and Stars in Their Eyes. In the 2000s he returned to acting, appearing in several West End productions, while also acting in some television roles.

Kelly's father and grandfather both served in the Navy. As a child, Kelly lived on Primrose Avenue in the town and became interested in acting when at the Urmston Musical Theatre, most notably playing the role of Louis in a production of The King and I in 1963. He continues to be President of the theatre group.

After 1961, Kelly went to Urmston Grammar School. He trained as an actor at The Manchester Metropolitan School of Theatre (formerly Manchester Polytechnic) and joined in a theatre group which included Julie Walters and Pete Postlethwaite. After graduation, he made his professional debut at the Pavilion Theatre in Rhyl.^{[citation needed]} After this debut he appeared regularly at Liverpool's Everyman Theatre. He is a former member of the Workers' Revolutionary Party.