This week Pope Benedict is traveling to England to beatify John Henry Cardinal Newman, one of the most influential English Catholics in history. Among Catholics, the idea that is most associated with Cardinal Newman is his theory of the development of doctrine. This theory argues that over time the Church’s understanding of divine revelation grows and develops, deepening our knowledge of these truths of our faith. Today most Catholics accept this theory as correctly interpreting the history of the Church’s doctrinal teaching and see it as the practical application of the Holy Spirit’s guidance to all truth that Jesus promised (John 16:13).

But this was not the case in Newman’s time. When he first proposed this theory – in the late 1830′s, a few years before he became Catholic – his ideas were seen as quite radical. It was still twenty years until Darwin’s famous On the Origin of Species, which proposed evolutionary processes in the development of biological species, and the common understanding of history in Newman’s time was a strictly static one. Everyone believed that although time went on, most things basically stayed the same. This was true in Christian doctrine as well – what 19th century Catholics believed was identical to what 6th century or 3rd century Catholics believed. But Newman’s study of history – combined with his probing mind – realized that this is not the case; that, in fact, our understanding of divine revelation is not identical to a 6th or 3rd century Catholic’s understanding. The Church’s constant meditation on divine truths over the centuries – guided by the Holy Spirit – has led to a deeper understanding of those truth. How the Trinity was expressed in the 4th century was a development – and an improvement – from how it was expressed in the 2nd century.

Newman liked to compare the Church to a tree, which grows organically from a seed to a sapling to eventually a full-grown mature tree. The essence of the tree is the same, but its outward appearance does change. Likewise, the Church does teach the same truths today that it did in previous centuries, but our understanding of these truths has developed and therefore outwardly they may appear on the surface to be different.

Many in Newman’s time accused Newman of heresy on this point. They felt that any suggestion that our faith was not identical to the faith of a 3rd century Catholic meant that the content of the Faith had changed. In other words, both could not be correct. But Newman realized that what is true in microcosm is true in macrocosm as well. If an individual believer’s understanding of the faith grows and develops during his lifetime (and it should), then the combination of all individual believer’s understanding must also grow and develop.

What Newman also recognized during this study of the development of doctrine is that there must be some objective party which can determine if a new understanding is a legitimate development or an illegitimate heresy. How can we know that Arius’ teachings on Christ are heretical but the unscriptural word “homoousis” (used in the Nicene Creed) is doctrinally legitimate? Time and again, no matter the issue, Newman saw that it was Rome that made the correct determination in this regard. It was Rome that protected the faith from innovation but guided it in its development. Thus, shortly after completing his work Essay on the Development of Christian Doctrine, he followed his own developed understanding of the Faith and entered the Church of Rome.