Evolution: Thinking Clearly about Randomness

By Dr. Jeff Mirus ( bio - articles - email ) | Oct 11, 2005

When Cardinal Schönborn argued in July that Church teaching is incompatible with neo-Darwinism, he touched off a firestorm of journalistic incredulity. Was the Church now retreating from John Paul II’s statement that the theory of evolution is “more than a hypothesis”? Was the Cardinal rejecting Pope Pius XII’s teaching in Humani Generis that evolution was compatible with the Faith, barring only polygenism and the evolution of the soul? What could it all mean?

Schönborn’s Thesis

In a July 7th opinion piece in the New York Times, Cardinal Schönborn vehemently rejected the suggestion that “the Catholic Church has no problem with the notion of ‘evolution’ as used by mainstream biologists—that is, synonymous with neo-Darwinism.” Because neo-Darwinians posit natural selection acting on random genetic variation as the mainspring of evolution, Schönborn asserted that “evolution in the Darwinian sense [is] an unguided, unplanned process of random variation and natural selection.” He concluded his argument by quoting a document on this very subject, Communion and Stewardship: Human Persons Created in the Image of God, issued by the International Theological Commission in 2004 under then Cardinal Joseph Ratzinger: “An unguided evolutionary process—one that falls outside the bounds of divine providence—simply cannot exist.”

Unfortunately, Cardinal Schönborn ignored the same document’s careful explanation of the fact that the scientific term random does not imply that a process is “unguided”. By ignoring this distinction, the Cardinal succeeded only in increasing the Catholic confusion over evolution.

Questions About Evolutionary Theory

There are many reasons for Christians to be cautious in their handling of evolutionary theory. Historically, the theory has frequently been used to justify materialism and atheism, abetting modern man’s flight from God. It has suited the temper of modern times well enough to be given a largely uncritical reception in many quarters. And in the wrong hands it is often transmuted into a philosophical world view. But as Pius XII pointed out, none of this baggage is essentially linked to the theory, which is not in itself incompatible with Faith. Indeed, many devout Catholic scientists are convinced that evolutionary theory provides the description of biological development most consistent with the available evidence.

It is, of course, part of the nature of scientific theories to be provisional and to be revised toward greater accuracy as more information accumulates. Science is doubtless in its infancy in understanding human origins, and not all scientists (and even fewer publicists) handle the provisional nature of their theories with sufficient scientific and philosophical care. Moreover, evolutionary theory in particular is exceedingly difficult to verify because it deals in large part with processes and events which are not directly observable. For these reasons, various competing theories are not only criticized from the outside but continue to be debated within the evolutionary camp. Nonetheless, the vast majority of scientists accept the importance of neo-Darwinian mechanisms in the history of life, and the case for randomness in genetic mutations is widely regarded as very strong.

Providential Randomness

Because of the importance (if not the certainty) of neo-Darwinian theory, it is vital that Christians understand that “chance” in the scientific sense does not in the least undermine the Christian understanding of Providence. In this discussion, I am indebted to Stephen M. Barr’s article “The Design of Evolution” in First Things (October 2005). Barr rightly points out that the notion of “chance” in science is precisely “statistical randomness”. Statistical randomness is based on nothing more than a lack of correlation among things or events which can still be helpful in understanding reality through the use of probability theory. We have statistical randomness in our world because, as Barr puts it, events “do not march in lockstep” but “are part of a vastly complex web of contingency.”

Now contingency is such an important part of the Catholic intellectual tradition that it is necessary to quote Communion and Stewardship at length to better realize how Catholic thought fits in with the scientific notion of randomness:

Many neo-Darwinian scientists, as well as some of their critics, have concluded that if evolution is a radically contingent materialistic process driven by natural selection and random genetic variation, then there can be no place in it for divine providential causality. But it is important to note that, according to the Catholic understanding of divine causality, true contingency in the created order is not incompatible with a purposeful divine providence. Divine causality and created causality radically differ in kind and not only in degree. Thus, even the outcome of a purely contingent natural process can nonetheless fall within God’s providential plan.

Communion and Stewardship goes on to quote Thomas Aquinas to emphasize how integral this understanding of contingency is to a coherent Catholic worldview. Some 700 years ago Thomas stated: “The effect of divine providence is not only that things should happen somehow, but that they should happen either by necessity or by contingency. Therefore, whatsoever divine providence ordains to happen infallibly and of necessity, happens infallibly and of necessity; and that happens from contingency which the divine providence conceives to happen from contingency.” For this reason, the International Theological Commission points out that “neo-Darwinians who adduce random genetic variation and natural selection as evidence that the process of evolution is absolutely unguided are straying beyond what can be demonstrated by science.” Needless to say, Christians who are concerned that such randomness must be denied to preserve their Faith are guilty of the same misconception on the other side.

Please, Give Me an Example

The density of these concepts may leave many readers crying out for an illustration. How can we conceive of statistical randomness as compatible with Divine Providence? Barr offers two necessarily incomplete analogies which may be useful. First, consider license plates on passing cars. The sequence of states exhibits a certain randomness in that observing a particular car from a particular state tells us nothing about where the next car will come from. Yet the trips of all the cars are planned, and each has a specific destination. Second, consider prose, which has lines with final syllables that do not rhyme. Because the ending syllables of these lines do not exhibit a particular kind of correlation (with respect to rhyming, they are “statistically random”), this does not mean the sentences are unplanned.

Thus God can impose various kinds of correlations on various kinds of events—or not—without the least reflection on His planning ability. The very possibility of an evolutionary process which could produce the kind of creatures that populate our world presupposes a universe with a very particular (and rather special) character. The God who created this universe is more than capable of working with extremely complex and apparently diffuse mechanisms, achieving very particular ends through a vast web of contingencies which we are unable to correlate. There is, in fact, much to suggest that the God we know and love prefers to work indirectly, through a variety of instrumental causes, and with a degree of complexity which very often defies our observational abilities.

The existence of “randomness” in the scientific sense therefore says nothing at all about the philosophical concept of intelligent guidance or the theological concept of Providence. The best scientists, of course, will not make the mistake of suggesting that statistical randomness points to an unguided universe. But for exactly the same reason, the best theologians will not feel constrained to defend their faith by denying the validity of scientific observations on specious spiritual grounds. In other words, there is no need for a quarrel when careful thought will suffice.