I took a class this past semester on the thought of Blessed Cardinal John Henry Newman, a popular 18th-century theologian who was beatified last fall during Pope Benedict's visit to England.

Our Pope is a great fan of Cardinal Newman's work, especially his autobiography, "Essay in Aid of a Grammar of Assent and Apologia Pro Vita Sua."

Though raised as an Anglican, Newman subscribed to Calvinist theology for a while, and eventually became Catholic. He was well-read and was a systematic and clear thinker - a good complement to the rationalistic and scientific age in which he lived.

Newman belongs to a great history of thinkers who help us to understand and defend our faith within the discipline of "systematic theology."

In his "Essay on the Development of Christian Doctrine," Newman shows we must have an awareness of development in our world, in the sciences and in our faith. He does this in order to protect against ideas of discontinuity with the past - that we do things differently now and are out of communion with our ancestors.

Development in Church practice and doctrine happen, but corruptions (for instance, literal interpretation of Scripture or merely symbolic understanding of the sacraments) also occasionally happen. Newman maintains that the Church has been given a minister - the Pope - to guarantee developments which are in continuity with the past and to guarantee against corruptions of doctrine.

The Pope's role is to maintain unity - not just between different Catholic cultures throughout the world, but across the centuries.

At times, there are corruptions within the Church instead of developments, but they usually die out because they are not commensurate with the rest of revealed truth and its authentic development.

Newman spends much of this book on the marks of true development compared to corruptions. He wrote it in order to dialogue better with other Christian denominations. Much of Newman's work was in apologetics. Since he had been a Calvinist and an Anglican, he knew very well the theologies against which he had to defend.

It's important these days, with the growing number of ex-Catholics in America and the growing number of evangelical churches springing up, that we be able to make a defense of our faith and to speak intelligently about it - especially to these groups.

My seminary formation incorporates this, but it must take hold in the wider culture. Catholics were better at evangelization in the past. We have the great examples of the Jesuit and Franciscan missionaries in the New World, including our "local saints" memorialized at the Shrine of Our Lady of Martyrs in Auriesville.

We need to rediscover this important aspect of our mission as Catholic Christians. Typically, it is usually our converts who are better defenders of the faith than "cradle Catholics." Newman was one of them, and his and others' writings can help us to rebuild this culture of witnessing to our faith.

This is one of the main reasons he wrote a book on development of doctrine. He covers most of the hot-button issues between Catholics and Protestants: Mary and the saints, infant baptism, papal supremacy, the relationship between faith and works, the New Testament canon and purgatory.

His arguments are detailed - he even refers to obscure historical events of the first centuries CE - but they are excellent arguments. There are other, more readable authors who also take on these topics in a more straightforward manner, but this does not invalidate the enormous contributions which Newman and his great intellect made to the study and defense of the faith.

(Daniel Quinn is a seminarian who has been studying for the priesthood for the Diocese of Albany at St. Mary's Seminary in Baltimore; he will be ordained a transitional deacon May 28. He is a native of Holy Trinity parish in Johnstown.)

This is part of The Evangelist's ongoing series of reports from diocesan seminarians on their studies, work and development. To read previous installments, go to www.evangelist.org and search for "seminarian diary."