The controversies surrounding the recent Extraordinary Synod on the Family have often put me in mind of John Henry Cardinal Newman, the greatest Catholic churchman of the 19th century. Newman wrote eloquently on an extraordinary range of topics, including university education, the play between faith and reason, the nature of papal authority and the subtle manner in which we come to assent in matters of religion. But the arguments around the Synod compel us to look at Newman’s work regarding the evolution of doctrine.

When he was at mid-career and in the process of converting from Anglicanism to Roman Catholicism, Newman penned a masterpiece entitled “On the Development of Christian Doctrine.” In line with the evolutionary theories that were just emerging at that time—Hegel’s work was dominant in most European universities and Darwin’s “On the Origin of Species” would appear just a few years later—Newman argued that Christian doctrines are not given once for all and simply passed down unchanged from generation to generation. Rather, like seeds that unfold into plants or rivers that deepen and broaden over time, they develop, their various aspects and implications emerging in the course of lively rumination. It is assuredly not the case, for example, that the doctrine of the Trinity was delivered fully-grown into the minds of the first disciples of Jesus and then passed on like a football across the ages. On the contrary, it took hundreds of years for the seed of that teaching to grow into the mighty tree of Augustine’s formulations in the De Trinitate or Aquinas’s complex treatise in the first part of the Summa theologiae. Moreover, Newman felt that even those definitive theological achievements in turn develop and unfold as they are mused over, turned around, questioned and argued about. He concludes: “a real idea is equivalent to the sum total of its possible aspects.” And those aspects appear only in the course of time and through the play of the lively minds that consider them.

It is precisely in this context that Newman penned the most famous line of “On the Development of Christian Doctrine”: “In a higher world it is otherwise; but here below, to live is to change and to be perfect is to have changed often.” Ideas change because they are living things.

I realize that many, upon considering this view, will get nervous—as did many in Newman’s day. Does this mean that doctrine is up for grabs? Should we keep our dogmatic statements, as one cynical wag once put it, in loose-leaf binders? To get some clarity on this point, I would recommend that we delve a little further into Newman’s great book and examine the criteria that he laid out to determine the difference between a legitimate development (which makes the doctrine in question more fully itself) and a corruption (which undermines the doctrine). Newman presents seven in total, but I should like to examine just three.

The first is what he calls preservation of type. A valid development preserves the essential form and structure of what came before. If that type is undermined, we are dealing with a corruption. Mind you, type can be maintained even through enormous superficial changes, as, to use Newman’s own example, “a butterfly is a development of the caterpillar but not in any sense its image.” And by the same token, superficialities can remain largely unchanged even as the type utterly morphs, as happened, say, in the transition from the Roman Republic to the Roman Empire.

A second criterion is what Newman refers to as “conservative action upon its past.” An evolution that simply reverses or contradicts what came before it is necessarily a corruption and not a development. In Newman’s own words, an authentic development “is an addition that illustrates, not obscures; corroborates, not corrects the body of thought from which it proceeds.” In accord with this idea, Christianity could be seen as the development of Judaism, since it preserves the essential teachings and practices of that faith, even as it moves beyond them. Cardinal George Pell alluded to this principle when he said, during the recent Synod debates, “the Church does not do back-flips on doctrine.” So, for example, if a proposal were put forth at the Extraordinary Synod that simply contradicted the teaching of John Paul II in Familiaris consortio or Paul VI in Humanae vitae, it would certainly reflect a corruption.

A third criterion that Newman puts forward is what he calls “the power of assimilation.” Just as a healthy organism can take in what it can from its environment, even as it resists what it must, so a sane and lively idea can take to itself what is best in the intellectual atmosphere, even as it throws off what is noxious. Both total accommodation to the culture and total resistance to it are usually signs of intellectual sickness.

Now how does all of this apply to the Synod? Well, let’s consider the proposal made by Cardinal Walter Kasper regarding communion for the divorced and re-married. Is it an authentic development or a corruption of Catholic moral teaching and practice? Might I suggest that all of the disputants in that argument take a step back and assess the matter using Cardinal Newman’s criteria? Would Newman be opposed in principle to change in this regard? Not necessarily, for he knew that to live is to change. Would he therefore enthusiastically embrace what Cardinal Kasper has proposed? Not necessarily, for it might represent a corruption. As the conversation continues to unfold over the coming months, I think all sides would benefit from a careful reading of “On the Development of Christian Doctrine.”