Ramified Natural Theology in Science and Religion: Moving Forward from Natural Theology
Authors: Holder Rodney 
Published: November 2022

RAMIFIED NATURAL THEOLOGY IN SCIENCE AND RELIGION: Moving Forward from Natural Theology by Rodney Holder. New York: Routledge, 2021. 244 pages. Hardcover; $160.00. ISBN: 9780367373191. *"Natural theology" is the study of what can be learned about God from a consideration of the universe of nature, and it has often been used to support claims of God's existence. The theologian Richard Swinburne applied Bayesian probability theory to various aspects of natural theology in order to present a justification for God's existence that could be evaluated numerically. Such a method has a certain objectivity about it, he felt. Moreover, it can be applied further to support the specific claims of the Christian faith through a similar treatment of historical facts given in the Bible. This latter effort he called "ramified natural theology," and it is the subject of the present book by Rodney Holder, who held a DPhil from Oxford in astrophysics before being ordained into the Anglican ministry. *This approach to Christian teaching is to be contrasted with those that are based on taking the scriptures as doctrinally authoritative in themselves, as exemplified by the position of Karl Barth. With ramified natural theology, the scriptures must be regarded as historical documents written in good faith by the authors of the time--just as any historian would normally assume about any historical documents--but with the proviso that supernatural events such as miracles are to be accepted as possible. That is something that academic historians will not allow, and it marks a key difference between the two disciplines. Arguing from a historic basis of the scriptures is, of course, not new. What is more innovative is to combine this with a consideration of natural theology, and to use a common analytical technique such as Bayesian theory to assign overall probabilities to the truths of central Christian beliefs. *Bayesian probability theory is a well-established technique. A good illustration would be of a doctor who is visited by a patient displaying symptoms that could come from one of several diseases. But which one? It is known from published statistics what is the a priori probability for a given citizen to have each of these diseases, and the probability for each of them to give the reported set of symptoms. From this information, the doctor can multiply the numbers together to obtain the relative probabilities that the patient has each of the possible diseases. The Bayesian formula allows the doctor to quantify the relative importance of each symptom and find the most likely diagnosis. *This approach can also be used to give believability estimates for more-abstract propositions. For each alternative proposition under consideration we must propose an a priori believability, taken to resemble a probability. We then consider the likelihood that each of the propositions could give rise to a set of given observations, and we finally apply the Bayesian formula. This may persuade us that one initial proposition is much more believable than another, but it does depend on the formation of numerical estimates of believability. These might be objective numbers that we do not know very well, or they may be intrinsically subjective in nature. It seems to me that the most important cases are unavoidably subjective, but quantifying one's degree of belief may be helpful in order to make progress. *Holder applies this type of analysis to the philosopher David Hume's skeptical evaluation of miracles. Hume argued that for a reported miracle, the proposition that it is mistaken is always more probable than the proposition that it is true--but we can put some numbers into this. Suppose that there is testimony T that a given miracle M has occurred, and that God G is proposed as the source of this miracle. Holder calculates a formula which I write here (slightly re-expressed) in order to give a flavor of the contents of the book: P(G|T) = P(G) {P(M|G) + P(T|~M)} / {P(G) P(M|G) + P(T|~M)}. *This is to be interpreted as saying that the probability that God is the source of the miracle as attested, P(G|T), is to be evaluated in terms of three quantities: the a priori likelihood of God's existence, P(G), the probability that God will perform this miracle, P(M|G), and the probability P(T|~M) that this testimony will be obtained when such a miracle did not occur (Hume's mistaken testimony). These numbers are clearly uncertain, but if we are sufficiently confident in the smallness of P(T|~M), and are willing to believe that God may perform miracles, then even a small initial belief in God can be enhanced by a large numerical factor by the testimony of the miracle. *Holder begins his account by discussing the natural theology of God as the First Cause of the universe and of its apparent physical fine-tuning to give intelligent life. Fuller accounts of these subjects have been given elsewhere (including in my own book) and can be referred to. Holder is concerned to provide enough information to justify the application of the Bayesian method to support a proposed belief in God, but most chapters in the book use Bayesian method to support belief in the Christian teaching of the death and resurrection of Jesus, using as factual evidence the material recorded in the Gospels and in other places. Extremely high levels of credibility can be claimed using this method, which can be combined with the natural theology arguments. Holder argues that the conclusions follow convincingly even when the assumptions and numerical probabilities that are used are allowed to vary considerably. *There are, however, some deficiencies in the Bayesian method that may impede its use. It might be questionable, as Holder accepts, to take the different pieces of evidence for the Resurrection in the New Testament as independent witness accounts. This they probably are, I would happily agree, but a determined skeptic might want to write off entire accounts at one go. After all, the later church had no hesitation in dismissing the so-called apocryphal gospels--for good reasons, needless to say--but we must be justly confident that the accepted gospels are the genuine article. Since the main reason that skeptics usually have for doubting this is that they disbelieve the contents, their argumentation may often seem circular. Holder is quite good at rejecting the methodology of skeptical scholars such as Bultmann. *A more serious problem is that the Bayesian method cannot convince the total skeptic. That is, if someone's initial belief value of a proposition is zero, then multiplying this value by a large numerical Bayesian factor will still give zero. For this reason, as Holder states but perhaps not strongly enough, the employment of another method such as "inference to the best explanation" may be indispensable. In this way, one might perhaps convince the skeptic to accept some kind of nonzero likelihood of God after all, and then the Bayesian method may help--at least to make it clear that evidence can indeed be cumulative and can be used to give ordered reasons for belief when strong enough. But the total skeptic may require a different kind of approach. Hume simply disbelieved in miracles. There are people today who likewise disbelieve in miracles, and there are those today who would likewise reject them "on principle," whatever the evidence presented. *Even with these reservations, the Bayesian method provides a healthy contrast to the kind of vagueness that often seems to beset theological discussion. It proposes attributing defined numerical values to all quantities and evaluates their consequences. Even if the reader is unconvinced by the method's claimed precision, it does at least give a clear indication of where a well-specified argument is capable of leading. *Even without the Bayesian aspects, the book is useful in collecting together quite a lot of material that is relevant for presenting the Christian faith. I would, however, point to two areas that are not very well covered. One is the entire topic of biological evolution, which has been the subject of so much familiar controversy and really needs a bit of clear discussion to decide whether it adds to the natural theology. The other is that incidental textual details found in the New Testament are themselves capable of adding considerably to our belief in the documents' historical authenticity. F. F. Bruce and, more recently, Peter Williams have published accessible studies of this, and it is an area that strongly merits being taken into consideration. *Throughout the book Holder's writing is clear and readable, although some of the on-the-fly references to various philosophers and theologians might frustrate a beginner. One must digest a fair bit of mathematics at the level illustrated above. It seems to me that, on the whole, the book is a graduate-level text whose hefty price-tag (even the e-version is not inexpensive--$48.95) will deter many potential readers. Still, within its given remit and despite a few limitations, the book does a good job. It can be well recommended for theological libraries and researchers in the area. I suspect, however, that the conclusions may need to be de-mathematized a little in order to convince ordinary citizens. *Reviewed by Peter J. Bussey, Emeritus Reader in Physics at the University of Glasgow, Glasgow G12 8QQ, UK.