Intelligent Design

Exposing the Hoary History of Methodological Naturalism: Does it really go back to the Middle Ages?

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In Part One of my series on methodological naturalism, I addressed the question: Is methodological naturalism a defining feature of science?. In Part Two, I rebut the oft-heard claim that even as far back as the Middle Ages, natural philosophers espoused a form of methodological naturalism. Proponents of this claim commonly cite passages in the works of medieval natural philosophers, which sound as if they are supporting this principle. I show that in fact, they were supporting two other methodological principles, which when combined, lead to conclusions which could easily be mistaken for methodological naturalism by a careless reader. Because these philosophers followed Aristotle in (i) defining science as the systematic study of natural bodies in motion, and (ii) limiting science to to the study of regularly occurring phenomena, they concluded that only natural causes could serve as proximate explanations for observed phenomena; in other words, miraculous events fall outside the scope of science. At first blush, that sounds a lot like methodological naturalism, but it’s actually a trivial conclusion, which follows from these philosophers’ restricted definition of science as the study of the general causes of natural phenomena. However, it could be argued that these medieval philosophers’ methodological principles were too narrow, as they would also exclude singular phenomena (such as the origin of life or the Big Bang) from the domain of science.

The only Christian medieval philosopher I can discover who explicitly declared that the existence of God lies outside the scope of “natural philosophy” (as science was then called) is St. Albert the Great, who held that only metaphysics could demonstrate the existence of God as an Ultimate Mover of the cosmos. That does not make St. Albert a methodological naturalist: as we’ll see, he argued that the celestial orbs were moved by intelligent beings – not by pushing, but simply by exercising their intellects. He also believed in miracles. Hence he did not hold that science was an autonomous discipline, as today’s scientists do; rather, he simply had a modest conception of its proper scope.

I go on to show that even on the narrow, Aristotelian definition of science as the study of regular natural occurrences, medieval Christian philosophers still felt impelled to invoke God, the incorporeal Unmoved Mover, as an ultimate explanation of changes occurring in the natural world. In other words, God still played a vital role in medieval science. I conclude that medieval philosophers were anything but methodological naturalists, and I cite passages from the works of St. Thomas Aquinas, John of Sacrobosco, Jean Buridan and Bishop Nicole Oresme, which conclusively show that they viewed God-talk as having a perfectly legitimate and even a vital role in science.

1. Was Methodological Naturalism already an accepted principle of science in the Middle Ages?

(a) Arguments in support of the view that Jean Buridan and Nicolas Oresme espoused Methodological Naturalism

Ronald Numbers, who is widely regarded as one of the leading experts on the history of creationism, argues that while the term “methodological naturalism” may be of recent origin, the principle underlying it goes back much further. He writes:

The phrase “methodological naturalism” seems to have been coined by the philosopher Paul de Vries, then at Wheaton College, who introduced it at a conference in 1983 in a paper subsequently published as “Naturalism in the Natural Sciences,” Christian Scholar’s Review, 15(1986), 388-396. De Vries distinguished between what he called “methodological naturalism,” a disciplinary method that says nothing about God’s existence, and “metaphysical naturalism,” which “denies the existence of a transcendent God.”

(p. 320 of: Ronald L. Numbers, 2003. “Science without God: Natural Laws and Christian Beliefs.” In When Science and Christianity Meet, edited by David C. Lindberg, Ronald L. Numbers. Chicago: University Of Chicago Press, pp. 265-285.)

Jean Buridan: an early exponent of methodological naturalism

Numbers contends that methodological naturalism was recognized as a principle of science as far back as the Middle Ages. The principle invoked a distinction between primary causes (i.e. God, the Creator) and secondary causes (i.e. natural agents).

By the late Middle Ages the search for natural causes had come to typify the work of Christian natural philosophers. Although characteristically leaving the door open for the possibility of direct divine intervention, they frequently expressed contempt for soft-minded contemporaries who invoked miracles rather than searching for natural explanations. The University of Paris cleric Jean Buridan (ca. 1295-ca. 1358), described as “perhaps the most brilliant arts master of the Middle Ages,” contrasted the philosopher’s search for “appropriate natural causes” with the common folk’s erroneous habit of attributing unusual astronomical phenomena to the supernatural. (Numbers, 2003, p. 267)

In a similar vein, John Farrell, author of The Day Without Yesterday: Lemaître, Einstein and the Birth of Modern Cosmology, contends in an online blog post entitled, A Problem of Credibility (Thursday, September 13, 2007), that Jean Buridan was a methodological naturalist:

Jean Buridan, the cleric and philosopher of the mid 1300s whose influence on medieval science and philosophy was, for quite some time, more widespread in Europe than that of Aquinas or Albert the Great, wrote in his Quaestiones super quattuor libris de caelo et mundo, “In natural philosophy one should consider processes and causal relationships as if they always came about in some natural fashion; therefore, God is no less the cause of this world and of its order, than if this world were eternal.” [emphasis mine]

That sure sounds like methodological naturalism to me. It’s also common sense.


Nicole Oresme: another methodological naturalist

Portrait of Nicolas Oresme, a renowned medieval bishop, mathematician, scientist, philosopher and economist, who is often falsely portrayed as a 14th century advocate of methodological naturalism by opponents of Intelligent Design. Miniature from Nicole Oresme’s Traite de l’espere, Bibliotheque Nationale, Paris, France, fonds francais 565, fol. 1r. Image courtesy of Wikipedia.

Nicole Oresme is also commonly cited as an example of a medieval natural philosopher who endorsed methodological naturalism. To quote Ronald Numbers again:

In the fourteenth century the natural philosopher Nicole Oresme (ca. 1320-82), who went on to become a Roman Catholic bishop, admonished that, in discussing various marvels of nature, “there is no reason to take recourse to the heavens, the last refuge of the weak, or demons, or to our glorious God as if He would produce these effects directly, more so than those effects whose causes we belive are well known to us.” (Numbers, 2003, p. 267.)

Professor Edward Grant, in his work, God and Reason in the Middle Ages (Cambridge University Press, 2001), goes even further and attempts to portray Nicole Oresme as a methodological naturalist:

He always sought natural explanations (as these quotations show) and refused to invoke supernatural or unnatural explanations, such as God, or magic, or demons. Although Oresme seems to have believed that understanding the articles of faith, he never let his faith intrude into his natural philosophy. (Grant, 2001, pp. 202-203.)


2. Were Jean Buridan and Nicole Oresme methodological naturalists?

If Ronald Numbers is going to quote from Buridan and Oresme, then he really should cite them in their appropriate context.

(a) Jean Buridan was no methodological naturalist

Numbers asserts that the cleric Jean Buridan (ca. 1295-ca. 1358), “contrasted the philosopher’s search for ‘appropriate natural causes’ with the common folk’s erroneous habit of attributing unusual astronomical phenomena to the supernatural.” Here’s what Buridan actually said in his Questions on Aristotle’s Meteorology:

There are several ways of understanding the word natural. The first [is] when we oppose it to supernatural (and the supernatural effect is what we call a miracle). And it is clear that the meteorological effects are natural effects, insofar as they are produced naturally, and not miraculously… The philosophers, consequently, explain them by the appropriate natural causes; but common folk, not knowing of causes, believe that these phenomena are produced by a miracle of God, which is usually not true… [Emphasis mine – VJT.] Source: Nicole Oresme and the Marvels of Nature: A Study of his “De causis mirabilium” with Critical Edition, Translation and Commentary by Bert Hansen (Toronto: Pontifical Institute of Medieval Studies, 1985), p. 59.

Note the qualification: “which is usually not true.” That certainly leaves open the possibility of miracles. And let us note also that Buridan is talking about meteorology, not biology.

Now, it is certainly true that while Buridan, as a devout Christian, allowed that God could intervene in the natural order of events, he also insisted that “in natural philosophy, we ought to accept actions and dependencies as if they always proceed in a natural way” (Questions on De caelo, book 2, question 9, p. 164 (Moody edition).

However, this restriction of the scope of science does not make Buridan a methodological naturalist. The term “methodological naturalism” needs to be defined carefully. In my recent post, Is methodological naturalism a defining feature of science?, I reviewed seven definitions of “methodological naturalism” and gave reasons for rejecting them, before settling on an eighth. The seven definitions I rejected were as follows:

(a): Scientists shouldn’t resolve scientific questions by appealing to the tenets of revealed religions;
(b): Science is the study of physical phenomena which are found in Nature;
(c): Science is the study of regular phenomena (or alternatively, replicable phenomena);
(d): Scientists should look for natural explanations before invoking supernatural ones;
(e): Scientists should avoid appealing to miracles when accounting for physical phenomena;
(f): Scientists should look for natural proximate causes when attempting to account for physical phenomena; and
(g): Scientists should invoke only natural causes when attempting to account for physical phenomena.

The definition which I finally settled on was the following:

(h) When doing science, we should assume that natural causes are sufficient to account for all physical phenomena, and that for precisely this reason, all talk of the supernatural is banished from science.

The reason why I opted for this definition is that the raison d’etre of methodological naturalism is to protect the autonomy of science, as an intellectual mode of inquiry. Science’s autonomy is guaranteed only if its explanations of observed phenomena are fully adequate. Definitions (a) to (g) make no attempt to address this point: they are silent regarding the total adequacy of scientific explanations, and therefore fail to guarantee the autonomy of science, as a domain of inquiry.

If we look at the foregoing quotes from Jean Buridan, it is readily apparent that Buridan is merely asserting principle (e), that scientists should avoid appealing to miracles, when attempting to account for empirical phenomena – or equivalently, principle (f), the claim that scientists should confine themselves to natural causes, when attempting to account for observed phenomena. This claim still falls short of methodological naturalism (principle (h)), since: (i) it says nothing regarding the competence of science to explain the entire gamut of physical phenomena; and (ii) all it eliminates is scientific appeals to the supernatural, leaving it still open to a supernaturalist to maintain that observed phenomena also require a deeper, metaphysical explanation.

Commenting on a passage in Aristotle’s On Generation and Corruption (2.10.336b25-35; Oxford trans.), Buridan writes that “Aristotle wishes to declare here and in the second book of De Generatione how such an order is reasonably from God and how all existing things from God, both celestial and inferior, are harmonious with regard to the order that is to be perpetually conserved.” (Questions on De Caelo, bk. 2, qu. 10, pp. 171-172).

In saying this, he was typical of many late medieval natural philosophers, according to Edward Grant, author of God and reason in the Middle Ages (Cambridge University Press, 2001), some of which can be viewed online at here. What relevance does this have for intelligent design? Very little, in my opinion. Does it make Buridan a methodological naturalist? I would answer no, for two reasons. First, at the very most, all that the preceding passage would rule out is the occurrence of miracles, in accordance with principle (e) above – and as we have seen, Buridan believed in miracles, anyway.

My second reason relates to the theory of Intelligent Design, which rejects methodological naturalism. Even for those Intelligent Design proponents who happen to believe that God is the author of the patterns we observe in Nature which exhibit the hallmarks of design, it need not follow that the creation of these designs was a supernatural act. As far as Intelligent Design is concerned, scientists are welcome to search for natural pathways leading from simple forms to specified complexity. An ID proponent could, for instance, believe (if he/she wished) that the initial conditions of the primordial Earth were very finely tuned by God, in such a way as to make the emergence of life by natural processes inevitable (the front-loading scenario). Hence even if Buridan actually believed in a cosmic order which is perpetually conserved, this belief would have in no way committed him to methodological naturalism.


(b) Bishop Nicole Oresme wasn’t a methodological naturalist, either

As we saw above, Numbers depicts Bishop Nicole Oresme as a thoroughgoing naturalist, in his approach to science, in his 2003 essay, “Science without God: Natural Laws and Christian Beliefs”:

In the fourteenth century the natural philosopher Nicole Oresme (ca. 1320-82), who went on to become a Roman Catholic bishop, admonished that, in discussing various marvels of nature, “there is no reason to take recourse to the heavens, the last refuge of the weak, or demons, or to our glorious God as if He would produce these effects directly, more so than those effects whose causes we believe are well known to us.”

In order to understand what Oresme meant, we need to closely examine what he actually said in the Prologue to his treatise, On the Causes of Marvels (De causis mirabilium), also known as the Quodlibeta, composed around 1370:

In order to set people’s minds at rest to some extent I propose here, although it goes beyond what was intended, to show the causes of some effects which seem to be marvels and to show that these effects occur naturally, as do the others at which we commonly do not marvel. There is no reason to take recourse to the heavens, the last refuge of the weak, or demons, or to our glorious God as if He would produce these effects directly, more so than those effects whose causes we believe are well known to us. (Emphases mine – VJT.) (Source: Oresme, ibid., p. 137.)

Note the heavily qualified language used in the above passage. Oresme is simply invoking what we now know as Occam’s razor. He is arguing that we should not invoke supernatural explanations when natural ones will do the job. This is equivalent to principle (d) which I discussed in my recent post, Is methodological naturalism a defining feature of science? Such a claim in no way implies methodological naturalism, for it does not tell us whether science will ever be able to explain all observed phenomena, and it does not exclude the supernatural from the domain of science.

Let us now return to what Professor Edward Grant wrote about Nicholas Oresme in his work, God and Reason in the Middle Ages (Cambridge University Press, 2001):

He always sought natural explanations (as these quotations show) and refused to invoke supernatural or unnatural explanations, such as God, or magic, or demons. Although Oresme seems to have believed that understanding the articles of faith, he never let his faith intrude into his natural philosophy. (Grant, 2001, pp. 202-203.)

Here, Grant is claiming that for Oresme, supernatural explanations lay outside the domain of science. However, the term “supernatural explanations” is ambiguous. Does it simply refer to miracles, or does it to any explanation which posits a supernatural agent at the end of a causal chain – e.g. God as an Unmoved Mover? The latter interpretation makes no sense, as it contradicts what Oresme’s own writings: in his work, Le Livre du ciel et du monde, he explained the movement of the spheres in terms of the action of intelligences (i.e. God and the angels).

If by “supernatural explanations” Grant simply means miracles, then all he is claiming is what I referred to as principle (e) in my recent post, Is methodological naturalism a defining feature of science?, which states that scientists should avoid appealing to miracles, when attempting to account for empirical phenomena. But as we saw, that an observed phenomenon is not miraculous does indeed entail that it is explicable in naturalistic terms, but that does not guarantee that it is explicable in purely naturalistic terms. It might still require God as an ultimate explanatory cause. If it does, then science cannot exclude talk of the supernatural after all.

Oresme did not espouse the claim that science is autonomous, which is pivotal to methodological naturalism

But let us suppose that by “supernatural explanations” in the passage quoted above, Grant means any reference to supernatural causes, as either ultimate or proximate explanations. On this construal, Oresme would be making a claim equivalent to principle (f) in my recent post, Is methodological naturalism a defining feature of science? – i.e. the claim that scientists should confine themselves to natural causes, when attempting to account for empirical phenomena. As I argued in my last post, even this claim is not equivalent to methodological naturalism, since: (i) it says nothing regarding the competence of science to explain the entire gamut of physical phenomena; and (ii) all it eliminates is scientific appeals to the supernatural, leaving it still open to a supernaturalist to maintain that observed phenomena also require a deeper, metaphysical explanation which goes beyond the phenomena themselves, to some underlying non-physical Cause. Methodological naturalism, as we argued above, goes further: it asserts that science is capable of fully explaining phenomena as such. Only then can the domain of science be guaranteed full autonomy, as an intellectual mode of inquiry. As I put it in my previous post on methodological naturalism: “If the empirical phenomena which science deals with cannot be fully explained within a scientific framework, but also require a theistic metaphysical framework in order to fully explain them, then the domain of science can no longer be isolated from that of theology, and science is no longer self-contained as a mode of inquiry.”

Oresme’s Aristotelian restriction of the scope of science: even one-off singular occurrences were excluded from scientific inquiry

Much has been made of Oresme’s reluctance to invoke miracles in natural philosophy. However, what is often overlooked is that for Oresme and his contemporaries, singular occurrences fell outside the domain of science, which was properly speaking about classes of events. As Loraine Daston explains in her article, Marvelous Facts and Miraculous Evidence in Early Modern Europe (Critical Inquiry, Vol. 18, No. 1, Autumn, 1991, pp. 93-124), this was because Aristotle Oresme excluded from the domain of science not only supernatural phenomena but also preternatural phenomena (rare and marvelous events, such as prodigies, which occur in a natural fashion):

As we have seen, preternatural phenomena, even when free of many portentous associations, had been in principle excluded from scholastic natural philosophy: scientia, properly speaking, was the corpus of demonstrated, universal truths, and preternatural phenomena were by definition exceptions to “that which is always or of that which is for the most part.” Neither Aristotle nor his medieval followers denied the existence of such oddities, but they did deny that anomalies resulting from chance and variability could form the subject matter of true science, for “there can be no demonstrative knowledge of the fortuitous.” Nicole Oresme’s De causis mirabilium (ca. 1370) shows how it was possible for Scholastic philosophers to simultaneously maintain that individual prodigies were wholly natural but nonetheless not susceptible to scientific explanation: “Therefore these things are not known point by point, except by God alone, who knows unlimited things. And why does a black hair appear on the head right next to a white one? Who can know so small a difference in cause?” Well into the seventeenth century, natural philosophy continued to restrict its investigations to common experience. (1991, p. 109.)

42. Aristotle, Metaphysics, 1027a20-27.
43. Aristotle, Posterior Analytics, 87b 19-20.
44. Hansen, Nicole Oresme and the Marvels of Nature, p. 279.
45. See Peter Dear, “Totius in verba: Rhetoric and Authority in the Early Royal Society,” Isis 76 (June 1985): 145-61, and “Jesuit Mathematical Science and the Reconstitution of Experience in the Early Seventeenth Century,” Studies in History and Philosophy of Science 18 (June 1987): 133-75, on the transformation of the scholastic conception of experience.

What this means is that Oresme, like other Aristotelian philosophers in his day, accepted what I referred to as principle (c) in my recent post, Is methodological naturalism a defining feature of science? – i.e. the claim that science is limited to the study of regularly occurring phenomena. But as we saw above, a scientist can accept this principle without committing him/herself to methodological naturalism. The reason why principle (c) fails to qualify as a genuinely naturalistic principle is that it only deals with the subject matter of science, which is defined as all regular or replicable natural phenomena. To rule out appeals to the supernatural, we need to limit not only the subject matter, but also the kinds of explanations that can be legitimately invoked in order to account for it. Aristotelian science was by definition supernaturalistic, as it required an incorporeal Unmoved Mover to account for any movements occurring in the cosmos.

The point I want to make here is that if this was Oresme’s framework for doing science, then his exclusion of miracles should occasion no surprise whatsoever. Since he is endeavoring to explain whole classes of phenomena, then it is perfectly obvious he will not be interested in invoking singular occurrences (such as “acts of God”) in order to account for them. However, Oresme’s scientific methodology is scientifically limiting: it is by definition incapable of accounting for singular “origin” events occurring in the past, such as the origin of the first living cell.

Oresme’s astronomy: firmly centered on God

In any case, it is quite certain that Nicole Oresme, whose cosmology was substantially Aristotelian, firmly believed that science required God as an ultimate explanatory cause, for his system of celestial spheres still needed an Unmoved Mover. Interestingly, the illuminator of Nicole Oresme’s Le livre du Ciel et du Monde, a translation of and commentary on Aristotle’s De caelo, produced for Oresme’s patron, King Charles V, drew the celestial spheres in the conventional order, with the Moon closest to the Earth and the stars highest, but the spheres were concave upwards, centered on God, rather than concave downwards, centered on the Earth. Below this figure, Oresme quotes the Psalms that “The heavens declare the Glory of God and the firmament showeth his handiwork.” There is a popular saying that a picture is worth a thousand words, so I’d like to reproduce this picture below.

Illustration of the Celestial spheres, from Le livre du Ciel et du Monde, by Nicole Oresme. Paris, Bibliotheque Nationale de France, Manuscrits, Fr. 565, fo 69 (detail). Image courtesy of Wikipedia.

I would also like to point out that Oresme discusses God and/or the faith in no less than 18 of 44 questions in his commentary, Questions on De Anima, which discussed Aristotle’s writings on the soul. (See Peter Marshall, Questiones super libros Aristotelis De Anima: A Critical Edition with Introduction and Commentary. Ph.D. dissertation, Cornell University, 1980.) In other words, Oresme believed that it was perfectly legitimate to discuss God, within the framework of Aristotelian psychology.

Finally, Professor Edward Grant, in a biographical essay on Nicolas Oresme in A Companion to Philosophy in the Middle Ages edited by Jorge J. E. Gracia, Timothy B. Noone (Wiley-Blackwell, 2005) acknowledges in passing that Orseme accepted the reality of Biblical miracles, including the miracle of Joshua’s long day, even as he argued in his scientific writings that this miracle could not be invoked to settle the question of whether the heavens revolved around the earth or whether the earth rotated daily on its axis:

To the Biblical argument that God aided the army of Joshua by making the sun stand still over Gibeon (Joshua 10:12-14), thus demonstrating that the heavens rotate and the earth is at rest, Orseme suggests that God could have also performed his miracle by temporarily halting the earth’s rotation. Both Galileo and Kepler presented explanations of the Joshua miracle, with Kepler’s argument resembling Oresme’s. (“Nicolas Oresme” by Edward Grant. In Gracis and Noone, 2005, p. 477.)

It should be readily apparent from the foregoing that Nicolas Oresme was no methodological naturalist.

(c) What would Buridan and Oresme have made of Intelligent Design?

Nevertheless, the reader still want to ask: what would Buridan and Oresme have made of Intelligent Design? That’s a fair question. Four points need to be borne in mind here.

1. At the time when Buridan and Oresme lived, Aristotle was the dominant intellectual influence. Aristotle held that the world was eternal, and that each species had always existed. Within his intellectual framework, the problem of how specified complexity arose – let alone how life originally arose – simply did not exist. Nothing arose, except individuals.

2. During the Middle Ages, abiogenesis (more accurately spontaneous generation) was widely believed to be a commonplace and everyday occurrence, as this Wikipedia article illustrates. Indeed, it was even believed that whole animals (e.g. crocodiles) could be generated from inanimate matter such as mud. In keeping with Aristotle’s biology, it was also believed that the higher animals, which were naturally “generated from seed” and which were known as “perfect animals” due to their greater complexity, could not be generated from non-living matter.

3. Describing actions as if they “always proceed in a natural way” does not imply that they always proceed in an unintelligent way. “Natural” does not equate to “blind.”

4. As Grant points out (op. cit., p. 198), Buridan, as a natural philosopher, was concerned with what he called the “common course of nature” – i.e. regular events and not singular events. Scientists now consider the origin of life on Earth to have been a singular event, yet they continue to investigate this occurrence, as they should. In so doing, they have already moved beyond Buridan’s characterization of science as dealing only with regular occurrences.

I would argue that it is intellectually stultifying to limit science to the search for unintelligent explanations of natural phenomena. The world is a more interesting place than it was thought to be in the fourteenth century – or the nineteenth, for that matter. In the twenty-first century, scientists should not be shackled by invocations of dead philosophers. Rather, they should be free to boldly search for the best explanation of natural phenomena, and follow that search wherever it takes them – even if the best explanation turns out to be some kind of intelligent agency.


3. Supernaturalism in the most popular astronomical textbook of the Middle Ages: John of Sacrobosco’s On the Sphere of the World

Figure of the heavenly bodies – an illuminated illustration of the Ptolemaic geocentric conception of the Universe by Portuguese cosmographer and cartographer Bartolomeu Velho (d. 1568). Bibliotheque Nationale, Paris. Ptolemy’s geocentric model was popularized in John of Sacrobosco’s popular medieval astronomy text, On the Sphere of the World (c. 1230). Image courtesy of Wikipedia.

Readers might be surprised to know that the notion of the clockwork universe is not a product of the mechanistic science of the 17th century, but actually goes back to medieval times. The idea can be found in John of Sacrobosco’s early 13th-century introduction to astronomy, On the Sphere of the World (c. 1230), which was widely popular in the Middle Ages. Indeed, it was one of the most influential works of pre-Copernican astronomy in Europe, as it was required reading for students at all Western European universities for the next four centuries after it was published.

In his book, Sacrobosco spoke of the universe as the machina mundi, or machine of the world – an image which might appear to leave no place for the supernatural. However, if one reads the book, it becomes readily apparent that Sacrobosco regarded the universe as having been made in the likeness of an Archetype, or Idea in the Mind of God, Who disposed it to behave in a regular fashion. At the end of his book, Sacrobosco also suggested that the reported eclipse of the Sun at the crucifixion of Jesus Christ was a disturbance in the order of the machine of the world. Hence it could only have been a miracle.

The following extracts from Sacrobosco’s book illustrate the supernaturalism which pervades his work:



THE FOUR ELEMENTS. The machine of the universe is divided into two, the ethereal and the elementary region. The elementary region, existing subject to continual alteration, is divided into four For there is earth, placed, as it were, as the center in the middle of all, about which is water, about water air, about air fire, which is pure and not turbid there and reaches to the sphere of the moon, as Aristotle says in his book of Meteorology. For so God, the glorious and sublime, disposed.

THE HEAVENS SPHERICAL. There are three reasons why the sky is round: likeness, convenience, and necessity. Likeness, because the sensible world is made in the likeness of the archetype, in which there is neither end nor beginning; wherefore, in likeness to it the sensible world has a round shape, in which beginning or end cannot be distinguished. Convenience, because of all isoperimetric bodies the sphere is the largest and of all shapes the round is most capacious. Since largest and round, therefore the most capacious. Wherefore, since the world is all-containing, this shape was useful and convenient for it. Necessity, because if the world were of other form than round — say, trilateral, quadrilateral, or many-sided — it would follow that some space would be vacant and some body without a place, both of which are false, as is clear in the case of angles projecting and revolved….



THE TWO MOVEMENTS AGAIN. Be it understood that the “first movement” means the movement of the primum mobile, that is, of the ninth sphere or last heaven, which movement is from east through west back to east again, which also is called “rational motion” from resemblance to the rational motion in the microcosm, that is, in man, when thought goes from the Creator through creatures to the Creator and there rests.

The second movement is of the firmament and planets contrary to this, from west through east back to west again, which movement is called “irrational” or “sensual” from resemblance to the movement of the microcosm from things corruptible to the Creator and back again to things corruptible….



ECLIPSE DURING THE PASSION MIRACULOUS. From the aforesaid it is also evident that, when the sun was eclipsed during the Passion and the same Passion occurred at full moon, that eclipse was not natural — nay, it was miraculous and contrary to nature, since a solar eclipse ought to occur at new moon or thereabouts. On which account Dionysius the Areopagite is reported to have said during the same Passion, “Either the God of nature suffers, or the mechanism of the universe is dissolved.”


If the author of the most popular astronomy text of the Middle Ages felt free to refer to God in this fashion, then I think we may safely reject the idea that medieval scientists espoused any kind of methodological naturalism.


4. Was St. Albert the Great a methodological naturalist?

Image of St. Albert the Great (d. 1280) from a fresco of 1352 (in Treviso, Italy) by Tommaso da Modena (1326-1379). Courtesy of Wikipedia.

St. Albert the Great (c. 1200-1280) was a Dominican friar, a Catholic bishop and a Doctor of the Church, who was called “Magnus” (“the Great”) during his own lifetime, due to his reputation as a scholar and philosopher. He was also an immensely learned scientist and polymath, whose knowledge was unrivaled in his day.

Professor Edward Grant, in his work, God and Reason in the Middle Ages (Cambridge University Press, 2001), portrays St. Albert the Great as a theologian who strove to keep science and theology separate. Although he does not refer to St. Albert as a methodological naturalist, Grant nevertheless asserts that St. Albert (and his pupil, St. Thomas Aquinas) “both chose to keep the theologization of natural philosophy to a minimum” and that St. Albert’s “basic conviction” was that “unless unavoidable, theology should not intrude into natural philosophy” (2001, p. 192). However, if we look beyond Grant’s interpretive lens to the actual passages he cites from St. Albert’s writings, a somewhat different portrait emerges.


Let us consider the first piece of evidence put forward by Grant: a quotation from St. Albert on the science of physics, which he chooses to define as Aristotelian (Peripatetic) philosophers have done, without recourse to theology:

Pursuing what we have in mind, we must take what we term ‘physics’ more as what accords with the opinion of Peripatetics than as anything we might wish to introduce from our knowledge … for if perchance we should have any opinion of our own, this would be proffered by us (God willing) in theological works rather than in those on physics. (Cited in Grant, 2001, p. 192.)

Grant draws the following moral:

Albertus thus believed that Aristotle’s natural philosophy was to be treated naturally, in the customary manner of Peripatetics. Where theological issues might be involved, they were to be treated in theological treatises. (2001, p. 192)

Grant is conflating two claims here – neither of which is equivalent to methodological naturalism. First, he declares that “Aristotle’s natural philosophy was to be treated naturally,” without telling us what that means. If it means (as Aristotle contended) that the proper subject matter of physics is natural bodies, then a supernaturalist could readily agree. As we saw in my recent post, Is methodological naturalism a defining feature of science?, this is simply equivalent to principle (b), which that defines science as the systematic study of physical phenomena. Such a claim poses no threat to supernaturalism, as it does not assert that science is competent to explain physical phenomena solely in terms of other physical phenomena, making the supernatural redundant. In any case, as we shall see below in our discussion of Aquinas, Aristotle’s physics was anything but naturalistic: it invoked an incorporeal Unmoved Mover to explain natural changes occurring in the heavens and on earth.

Second, Grant contends that for St. Albert, “theological issues” don’t belong in a book on natural philosophy but in a theological treatise. Grant is being vague here. If by “theological issues” he means matters of Divinely revealed faith (e.g. speculation about whether Jesus Christ violated the laws of physics when He fed the 5,000, or whether He accomplished the miracle in a less “disruptive” manner), then even a supernaturalist would agree that discussion of such issues does not belong in a physics text. But if by “theological issues” he means the existence of an Intelligent, Incorporeal Mover of the cosmos, then St. Albert would be defending principle (g): Scientists should invoke only natural causes when attempting to account for physical phenomena. That would take us much closer to methodological naturalism, but not all the way there. Because principle (g) does not assert that science is capable of completely explaining physical phenomena, it is incapable of safeguarding the autonomy of science from other disciplines, as an intellectual mode of inquiry. This, as we have seen, is the claim which distinguishes methodological naturalism.

So, which of the above two interpretations is correct? Unfortunately, Grant does not say.


A second piece of evidence cited by Grant is a passage in St. Albert’s Commentary on De caelo, where he discusses whether the heaven is ungenerable or incorruptible, then mentions that Jews, Christians and Muslims believe that it was created ex nihilo, and finally decides not to discuss this opinion in his commentary: “But with regard to this opinion, it is not relevant for us to treat it here.” (Book 1, tr. 1, ch. 8, col. 2-20, col. 1.) He then opts to discusses the opinion that “the heaven is generated from something preexisting,” even though it runs contrary to faith.

What Grant neglects to mention here is that in St. Albert the Great’s day, there was not a scintilla of scientific evidence that the world had a beginning. For St. Albert, the question of whether God could have made the world 6,000 years ago out of nothing, as he devoutly believed, would have had no place in a physics text of his day, since physics, insofar as it treats of God, deals not with what God can do in the abstract, but only with what He can be shown to have done, by the natural light of reason, as opposed to Divinely revealed faith. That, I would suggest, is the distinction that St. Albert draws. What he is saying here is quite different from the claim made by methodological naturalists, that God-talk has no place in science. Rather, St. Albert is asserting that we have no right to speculate about God’s powers in a physics text. We have to stick to the data provided by Nature.


A third item of evidence listed by Grant is taken from his Commentary on De caelo, where he treats of the vexed question of “whether there is one world or more.” In this passage, St. Albert concludes, on the basis of his understanding of Aristotelian physics, that “it is impossible that there be several worlds, or that more can be made.” He anticipates that some of his readers will rise the theological objection that “God could have made more worlds if He wished,” and he replies that “Here our understanding is about what is impossible and necessary with respect to the essential and proximate causes of the world.” St. Albert then continues: “And there is a great difference between what God can do by His absolute power and what can be done in nature [or by nature].”

This passage readily lends itself to the interpretation I suggested above, which states that it is not the business of physics to discuss what God can do in the abstract, but only with what He can be shown to have done, by the natural light of reason, as opposed to Divinely revealed faith. In other words, St. Albert is simply saying that we have no right to speculate about God’s powers in a physics text. We have to stick to the data provided by Nature.


A fourth category of evidence to which Grant attaches great weight concerns St. Albert’s infrequent references to God in his scientific writings:

Albertus kept theological references in his natural philosophy to a minimum, as is evident in his Aristotelian commentaries. In the 261 chapters that comprise the 8 books in his Commentary on the Physics, Albertus (deus and its variants) in 24, or in approximately 9 per cent of his chapters, and in the 111 chapters that make up the four books of his Commentary on De caelo, he mentions God in 9, or approximately 8 per cent of the total. Most of Albertus’s uses of the term God in his Commentary on the Physics are in direct response to Aristotle’s text, especially in the eighth book. Thus, of the 64 occurrences of primus motor, that is, first mover or God, 55 occur in book 8; of the 69 occurrences of causa prima, that is, first cause, or God, 37 occur in book 8; and of the 78 occurrences of deus, God, 40 occur in the eighth book.

Most of these occurrences are in direct response to Aristotle’s own mentions of God, or gods, or something about divinity. They have nothing to do with considerations of faith or theology.

In reply: first of all, it makes absolutely no difference whether St. Albert the Great referred to God 64 times, or 37, or 78, in his writings on physics. A single reference would be enough. That would suffice to show that St. Albert didn’t believe that God-talk has no place in science, as methodological naturalists contend. While Grant does not make the mistake of identifying St. Albert the Great as a methodological naturalist, he endeavors to show that St. Albert tried to keep God-talk to a minimum when doing science. But that claim just won’t wash. Either God-talk has a legitimate place in science or it does not. If it does, then it is perfectly proper to invoke God as a scientific explanation of phenomena, and as the ultimate explanation of all natural phenomena, God’s role can hardly be minimized. Surely St. Albert must have appreciated this point.

Second, Grant provides no evidence that it was ever St. Albert’s intention to keep “theological references in his natural philosophy to a minimum,” nor does he even bother to define the term “theological references.” Does he mean references to dogmas of the Catholic faith (which, as we have seen, St. Albert did not want to see included in physics texts), or does he simply mean references to God (Whose existence St. Albert held to be knowable by natural reason alone, unlike the dogmas of faith)?

Third, Grant’s assertion, that St. Albert the Great mentioned God in only 9 per cent of the chapters in his Commentary on the Physics, is worthless, in the absence of a comparison with: (a) other scientists of his day, whose references may have been even fewer for all we know; and (b) scientists from other periods – e.g. the seventeenth, eighteenth and nineteenth centuries. How often did they mention God in their physics texts? Grant doesn’t tell us.


Grant’s fifth and final item of evidence that St. Albert endeavored to minimize references to God in natural philosophy is that he fails to mention God in many passages where, as a theologian, he might have been expected to. For instance, in his lengthy commentary on the infinite, St. Albert refers to God only twice, declaring only that God is “not finite,” “not a body” and “not measurable.” Grant points out that “In theological treatises, it was common to involve God with space, place and vacuum” (2001, p. 194), but St. Albert does not do this in his discussion of space and the vacuum.

I have to say I am not persuaded by Grant’s reasoning here. What Grant forgets is that St. Albert was not writing a theological treatise, but a book on physics. Obviously, different ground rules apply in the two cases. The ground rule which I am suggesting St. Albert followed when doing natural philosophy is that God could be legitimately invoked to explain natural phenomena that can be shown to have occurred, if the natural light of reason points to Him as the ultimate explanation of those phenomena.


David Twetten on St. Albert the Great’s view of natural philosophy

In an article titled, “Albert the Great on Whether Natural Philosophy Proves God’s Existence” (Archives d’Histoire Doctrinale Et Littéraire du Moyen Âge 64:7-58 (1997) – abstract here), David Twetten contends that on St. Albert the Great’s view, only metaphysics can establish the existence of God:

Contrary to the prevailing view, Albert agrees with Avicenna that the existence of God is not proved by any science but metaphysics. Physics concludes merely to a first immobile cause intrinsic to what it moves, an intellectual being “conjoined” to the heavens: the “soul” of the outermost sphere. This doctrine, which is developed in Albert’s aristotelian paraphrases, is at least consistent with, if not also accepted within, Albert’s own thought.

Aristotle, in Book VIII of his Physics, reasons that there must be an incorporeal Unmoved Mover. For St. Albert’s pupil, St. Thomas Aquinas, “this everyone understands to be God,” and in his Summa Theologica I, question 3, he proceeds to argue that the Unmoved Mover must be Pure Act, utterly simple, and identical with its own act of existence. But unlike his pupil, St. Albert held that natural philosophy was incapable of establishing the existence of a transcendent Being. In a recent article co-authored with Steven Baldner and Steven Snyder, titled, “Albert’s Physics,” in A Companion to Albert the Great: Theology, Philosophy, and the Sciences (edited by Irven Resnick, Brill, Leiden, The Netherlands, 2013), Twetten concludes:

Thus, for Albert, physics concludes to a first cause of motion that is outside the genus of motion but that cannot be God. Its discussion ends once the argument arrives at an immediate unmoved incorporeal cause of the first corporeal change in classical astrophysics: a non-hylomorphic soul of the outermost self-moved heavenly sphere. (pp. 218-219)

Does this make St. Albert a methodological naturalist? No; all it means is that he had a modest conception of what kinds of questions could be resolved by science alone. We may conclude that St. Albert held to principle (g): Scientists should invoke only natural causes when attempting to account for physical phenomena. This is not because science is autonomous, but merely because it is the wrong tool for resolving metaphysical questions. I might add that there are many philosophers in the Intelligent Design camp who have argued for the same view: Dr. William Dembski, for instance, has frequently argued that science is incapable of deciding whether the Intelligent Designer is God or some natural intelligence. Yet no-one would describe Dembski as a methodological naturalist!

Why St. Albert could not have been a methodological naturalist

Finally, it should be borne in mind that despite his claim that natural philosophy could no establish the existence of God, St. Albert did believe that science (or natural philosophy) could establish the existence of various immaterial intelligences, which moved the celestial orbs, as well as an unmoving, intelligent and immaterial First cause, an intellectual being “conjoined” to the heavens. Albert believed that natural philosophy could also demonstrate that the human intellect is immaterial. In other words, St. Albert denied the causal closure of the physical – a vital part of methodological naturalism.

At first sight, it might not appear obvious that methodological naturalism implies a commitment to the causal closure of the physical. But if we maintain that when doing science, we should assume that natural causes are sufficient to account for all physical phenomena, and if by “natural causes” we mean “physical causes, with measurable properties including a location in space-time, which behave in accordance with the laws of Nature,” then it necessarily follows that we may not invoke non-physical causes when doing science – in which case, there is no place in science for immaterial intellects which possess some mysterious power to move bodies in a non-lawlike fashion. These considerations suggest that we should tighten the definition of methodological naturalism, as follows:

(h’) When doing science, we should assume that natural causes (i.e. physical entities behaving in accordance with the laws of Nature) are totally sufficient to account for all physical phenomena, and that for precisely this reason, all talk of supernatural, paranormal or non-physical entities is banished from science.

By this definition, then, St. Albert the Great’s natural philosophy is clearly at odds with methodological naturalism.

I’d like to conclude with quotes from two unimpeachable sources on the natural philosophy of St. Albert the Great. The first is a quote from the article on Albertus Magnus in the 1906 Jewish Encyclopedia, which contends that St. Albert was heavily influenced by the writings of the Jewish philosopher Maimonides:

Following Maimonides, who refutes the proofs produced by the Peripatetics concerning the eternity of the world (“Physics,” viii. 1, chap. xi.; “Summa Theologiae,” ii. 1, 4, 3; compare “Moreh,” ii. 14), Albertus is of [the] opinion that the eternity of the world must be rejected principally for this reason, that, if any one accepts the views of the Peripatetics, the world would have been evolved by natural force, and would, therefore, not be the work of a Creator acting with liberty and intention (“Physics,” viii. 1, chap. xiii.; compare “Moreh,” ii. 19, 24).

The foregoing quote, which cites St. Albert’s commentary on Aristotle’s Physics, shows that St. Albert was very concerned to keep science “God-friendly,” even though he held that science was incapable of demonstrating the existence of God. The last thing Albert wanted was a godless natural philosophy.

My second quote is from an address in English given by Pope Benedict XVI in Vatican Square, on 24 March 2010:

Albert was canonized and declared a Doctor of the Church by Pope Pius XI, and Pope Pius XII named him the patron of the natural sciences. Saint Albert shows us that faith is not opposed to reason, and that the created world can be seen as a “book” written by God and capable of being “read” in its own way by the various sciences. His study of Aristotle also brought out the difference between the sciences of philosophy and theology, while insisting that both cooperate in enabling us to discover our vocation to truth and happiness, a vocation which finds its fulfillment in eternal life.

But if the world is a “book” written by God, which the various sciences are meant to “read,” then St. Albert could hardly have viewed natural philosophy as an autonomous field of inquiry. Nor could he have envisaged the cosmos as being causally closed, thereby ruling out “acts of God.”

I conclude that Grant, in his portrayal of St. Albert as someone who tried to minimize the role of theology in science, is attempting to pigeon-hole the saint into a philosophical box which does not reflect St. Albert’s own thinking.


5. St. Thomas Aquinas on the legitimate place of God in science

Image of St. Thomas Aquinas (1225-1274) depicted in stained glass. Courtesy of Wikipedia.

St. Thomas Aquinas (1225-1274) is generally considered to be the Catholic Church’s greatest theologian and philosopher. Aquinas also wrote extensive commentaries on Aristotle’s scientific works, and was a student of St. Albert the Great, who as we have seen was an accomplished scientist. If I can demonstrate that Aquinas rejected the tenets of methodological naturalism, this should effectively puncture the myth that methodological naturalism was an accepted principle of medieval science.

I will be citing passages from Aquinas’ writings below. However, in order to refute any possible accusations that I am being selective in my citations, I would like begin by quoting from two Thomist scholars whose credentials are unimpeachable: the renowned scholars Ralph McInerny and John O’Callaghan, whose article, Aquinas appears in The Stanford Encyclopedia of Philosophy. The authors describe Aquinas’ view of natural science in the following terms:

The concern of natural science is of course natural things, physical objects, which may be described as “what come to be as the result of a change and undergo change.” The first task of natural philosophy, accordingly, is to define and analyze physical objects.
(McInerny, Ralph and O’Callaghan, John, “Saint Thomas Aquinas”, The Stanford Encyclopedia of Philosophy (Winter 2010 Edition), Edward N. Zalta (ed.), URL = The above quote is taken from section 6 of the article.)

This is precisely what Aquinas himself says in his Commentary on Aristotle’s Physics, where he writes:

3. … And because everything which has matter is mobile, it follows that mobile being is the subject of natural philosophy. For natural philosophy is about natural things, and natural things are those whose principle is nature. But nature is a principle of motion and rest in that in which it is. Therefore natural science deals with those things which have in them a principle of motion.

(Commentary on Aristotle’s Physics, Book 1, Lecture 1.)


At first blush, it might appear as though Aquinas is espousing a form of methodological naturalism here, but in fact, all Aquinas is saying is that the subject matter of natural science is physical objects. If we recall the various claims that we examined in my recent post, Is methodological naturalism a defining feature of science?, Aquinas’ claim here is equivalent to principle (b), whereas methodological naturalism (as we saw) makes a much stronger claim. The assertion that science is about physical objects in no way entails that scientific explanations have to be confined to natural objects. And in fact, Aquinas himself famously maintained (in his first proof of the existence of God in the Summa Theologica, I, q. 2, art. 3) that movement in the world could only be explained by positing an incorporeal Unmoved Mover as the ultimate explanation of motion. To quote McInerny and O’Callaghan again:

… But let us first lay out Thomas’s view of metaphysics. His question is Aristotle’s: is there any science beyond natural science and mathematics? If to be and to be material are identical, then the science of being as being will be identical with the science of material being. That is what Aristotle rejects in the passage just quoted. It is in the course of doing natural philosophy that one gains certain knowledge that not everything that is is material. At the end of the Physics, Aristotle argues from the nature of moved movers that they require a first unmoved mover. If successful, this proof establishes that there is a first mover of all moved movers which is not itself material. Furthermore, the discussion of intellect in On the Soul III to which we alluded in the preceding paragraph, points beyond the material world. If the activity of intellect provides a basis for saying that, while the human soul is the substantial form of the body, it can exist apart from the body, that is, survive death, it is an immaterial existent. The Prime Mover and the immortal souls of human beings entail that to be and to be material are not identical. Since these are acquisitions at the limit of natural philosophy, they represent possible objects of inquiry in their own right. This is pre-eminently the case with the Prime Mover.
(McInerny, Ralph and O’Callaghan, John, “Saint Thomas Aquinas”, The Stanford Encyclopedia of Philosophy (Winter 2010 Edition), Edward N. Zalta (ed.), URL = The above quote is from section 9.)

This is what Aquinas says in Book VIII of his Commentary on Aristotle’s Physics, where he writes:

1069. Having shown that in things moved by another there is not a process to infinity but a first must be reached which is either immobile or a mover of self, and having shown that, of a thing that moves itself, one part is an immobile mover, and that, consequently, in either case there is a first mover that is immobile, now, because among self-movers which exist among us, namely, perishable animals, it happens that the motion-causing part in the thing which moves itself is perishable and moved per accidens, namely, the soul, the Philosopher [Aristotle] wishes to show here that the first mover is imperishable and is not moved either per se or per accidens.

Commentary on Aristotle’s Physics, Book 8, Lecture 12

Later in the same lecture, Aquinas concludes that the Unmoved Mover is one:

1076. …Therefore, it is absolutely necessary that the first mover be one and perpetual. But an immobile mover that is moved per accidens is not perpetual, as has been said above. It remains, therefore, that the first mover is utterly immobile, both per se and per accidens.

Commentary on Aristotle’s Physics, Book 8, Lecture 12

These remarks are taken from Aquinas’ commentary on Aristotle’s Physics – and physics is, of course, a branch of natural philosophy. For Aquinas, then, science (or natural philosophy) can prove the existence of an Unmoved Mover of all material things, which is not itself material. Science can also show that the human intellect is not material. Both of these claims directly contradict the tenets of methodological naturalism.


In their article, McInerny and O’Callaghan carefully explain that in the teaching of St. Thomas Aquinas, science can arrive at an indirect knowledge of God:

… Separate substance, divine being, is not directly accessible for our inspection or study. We come upon our first secure knowledge of God in the proof of the Prime Mover. Tantalizingly, once seen as a necessary requirement for there being any moved movers, the Prime Mover does not become a thematic object of inquiry in natural philosophy. One obvious reason for this is that such an entity is not an instance of the things which fall under the scope of the science. Knowledge of it comes about obliquely and indirectly. The same restriction is operative when the philosopher turns his culminating attention to the deity. How can he know more about the first cause of things? If the Prime Mover is known through moved movers as his effects, any further knowledge of him must be through his effects. It is by describing the effect as widely as possible that one seeks to come to a knowledge of the first cause unrestricted by the characteristics of mobile things. That characterization is being as being. The subject of metaphysics is being in all its amplitude in order to acquire a knowledge of the cause of being that will be correspondingly unbounded. (Quoted from section 9.)
(McInerny, Ralph and O’Callaghan, John, “Saint Thomas Aquinas”, The Stanford Encyclopedia of Philosophy (Winter 2010 Edition), Edward N. Zalta (ed.), URL = Quoted from section 9.)

Our scientific knowledge of God, then, is indirect: we infer His existence from the study of bodies. But the key point here is that Aquinas recognizes that God’s existence is scientifically knowable. As William A. Wallace points out in his essay, St. Thomas’ Conception of Natural Philosophy and its Method (Studi Thomisti: La philosophie de la nature de St. Thomas d’Aquin: actes du Symposium sur la pensée de Saint Thomas, tenu à Rolduc, les 7 et 8 nov. 1981, ed. L. Elders, pp. 7-27):

“For St. Thomas there is no distinction between philosophia naturalis [natural philosophy – VJT] and scientia naturalis [natural science – VJT]: both philosophia and scientia are for him cognitio certa per causas [knowledge ascertained through its causes – VJT], and the essential difference between the Physics and the other natural treatises lies only in the [fact] that the former is concerned with a general analysis of nature and change whereas the latter are more specific and concrete in the subjects of their consideration” (p. 16).

This is an especially important point, since, as we have seen, Aristotle establishes the existence of the Unmoved Mover (whom Aquinas identified with God) in Book VIII of his Physics. Aquinas was emphatic that human reason alone could prove the existence of an Uncaused Cause (Summa Theologica I, article 2, question 2), and he even declared that the existence of God is “capable of being scientifically known and demonstrated,” since it “can be known by natural reason.” The notion that God falls outside the domain of science would have been utterly foreign to the thinking of St. Thomas Aquinas.

Finally, in his Summa Contra Gentiles Book III, chapter 99, paragraph 9 (That God Can Work Apart From The Order Implanted In Things, By Producing Effects Without Proximate Causes), Aquinas asserts that miracles can publicly manifest the power (and hence, the existence) of God:

[D]ivine power can sometimes produce an effect, without prejudice to its providence, apart from the order implanted in natural things by God. In fact, He does this at times to manifest His power. For it can be manifested in no better way, that the whole of nature is subject to the divine will, than by the fact that sometimes He does something outside the order of nature. Indeed, this makes it evident that the order of things has proceeded from Him, not by natural necessity, but by free will.

Here, Aquinas says that God’s power and voluntary agency “can be manifested in no better way … than by the fact that He sometimes does something outside the order of nature.” I conclude that he would have had no qualms whatsoever about appealing to supernatural effects, in order to convince skeptics of God’s existence.

From the foregoing quotations, it should be abundantly clear that Aquinas was not a methodological naturalist.

I hope that the evidence I have adduced above will discredit once and for all the absurd thesis that methodological naturalism was a recognized rule of science in the Middle Ages.


6. Was there a decline in supernaturalism after the Middle Ages?

In his 2003 essay, “Science without God: Natural Laws and Christian Beliefs” (in When Science and Christianity Meet, edited by David C. Lindberg, Ronald L. Numbers, Chicago: University Of Chicago Press) Ronald Numbers contends that supernaturalism gradually gave way to naturalism, following the end of the Middle Ages:

For ordinary folk the most compelling instances of supernaturalism giving way to naturalism occurred not in physics or chemistry but in such areas as meteorology and medicine, in explanations of epidemics, eclipses, and earthquakes. Already by the sixteenth century, supernatural explanations of disease had largely disappeared from medical literature except in discussions of epidemics and insanity, which remained etiological mysteries, and venereal diseases, the wages of sin. In writing about the common afflictions of humanity—fractures, tumors, endemic diseases, and such—physicians seldom mentioned God or the devil. Even when discussing the plague, the most dreaded disease of all, they tended merely to acknowledge its supernatural origin before passing quickly to its more mundane aspects. The great French surgeon Ambroise Pare (1510-90), for example, explicitly confined himself to “the natural causes of the plague,” saying that he would let divines deal with its ultimate causes. Priests and theologians may have placed greater emphasis on supernatural causes and cures, but in general they too easily accommodated new medical knowledge by maintaining that God usually effected His will through natural agencies rather than by direct intervention. Theological interests thus seldom precluded searching for natural causes or using natural therapies. (Numbers, 2003, p. 269.)

However, when we look at the historical evidence, we find that even during the Middle Ages, doctors explained epidemics such as the Black Death in natural terms. What’s more, educated people were accustomed to explaining earthquakes and eclipses as purely natural phenomena.

Did doctors in the Middle Ages explain epidemics as plagues sent by God?

Yersinia pestis (200x magnification), the bacterium which causes bubonic plague. Image courtesy of Wikipedia.

An article entitled, “Medicine, Theoretical”, in Medieval Science, Technology, and Medicine: An Encyclopedia edited by Thomas F. Glick, Steven John Livesey and Faith Wallis (Routledge: New York and London, 2005) describes how medieval physicians viewed disease, and demonstratively that they attempted to explain the Black Death in naturalistic terms, as a contagious disease, and not as a Divine visitation for sin:

In manuals of theory such as the Isagoge, … disease states are classified into three broad categories: (1) Mala complexio or disorders of temperament (humoral imbalance); (2) Mala compositio or congenital defect; and (3) Solutio continuatis, “breach of continuity” or trauma. Thus disease was not precisely an entity in Galenic medicine, but an event (accident) or state. Drawing on Aristotelian hylomorphism, doctors defined health and disease as “forms determining matter”; hence medieval physicians regarded as disease what a modern would term clinical presentation or symptom. Such disease specificity as exists in medieval medical theory lies closer to the modern concept of the syndrome: hence, a morbus was a disease of mala complexio with a proper name designating a particular cluster of symptoms (e.g. gout. leprosy, migraine). Ontologically, this was a fairly weak concept, because a morbus could manifest differently in patients of different complexion, and one morbus could change into another. Leprosy presented an interesting challenge to this model. Particularly in the fourteenth and fifteenth centuries, and apparently in response to increasing demands on the medical profession for expert opinion in accusations of leprosy, authors such as Gilbertus Anglicus and Jordanus de Turre concentrated on cataloguing the features of leprosy that were definitive and invariable. The Black Death posed a different kind of problem, for its universal scope defied the Hippocratic model of an epidemic as a local outbreak of acute and virulent disease. Learned commentators invoked cosmological explanations based on the notion of a global infectio or tainting of the atmosphere, with consequent poisoning of the soil, water, foodstuffs etc. over wide regions. Although plague might be caused by environmental factors, it was understood to spread through contact (contagio).

Earthquakes in the Middle Ages

It is widely assumed that people in the Middle Ages saw earthquakes as evidence of Divine displeasure. However, recent evidence suggests otherwise. A paper entitled, “Man and Natural Disaster in the Late Middle Ages: The Earthquake in Carinthia and Northern Italy on 25 January 1348 and its Perception” by Christian Rohr (Environment and History 9(2003): 127-149) discusses a major earthquake that occurred in Europe, at the time of the Black Death. I shall quote the abstract here:

How did people react to natural abnormalities such as earthquakes and floods in the Middle Ages? Why did they experience them as disasters? How did they explain them? Did they really see them as a divine punishment? Reports of the earthquake of 1348, which was followed by a landslide and a flood destroying the city of Villach, were often combined with accounts of the Black Death, which arose in these regions just a few weeks later.

There are still only a few studies of natural disasters in the Middle Ages, and for the eastern Alpine regions only the earthquake of 25 January 1348 has been examined in detail, albeit using a variety of approaches. This study tries to provide a mentality-bound approach, searching for the mentalities of the people, but without claiming to write a ‘history of mentalities’. Nevertheless, it seems easier to examine mentalities in extreme situations than in normal times, though the records concerning natural disasters in the Late Middle Ages are mostly brief.

By re-visiting the sources for the 1348 earthquake following the studies of Borst (1981) and Hammerl (1992) and looking at aspects of its perception, management and explanation, this article calls into question the supposed ‘medieval’ equation of natural disaster and divine punishment. In spite of the fact that the natural disasters and Black Death were mixed up in the sources, there is little evidence that the earthquake itself was experienced as anything other than something tremendous and unexpected, but which also belonged to daily life. (Emphases mine – VJT.)


A Witch’s Eclipse (1349)

I am indebted to for the following account of a medieval eclipse, which shows that educated people in the Middle Ages were well aware that eclipses were natural phenomena.

On June 30, 1349, there was a total eclipse of the Moon visible in London, which Archdeacon Churton connects with the following incident:

The worthy Archbishop Bradwardine, who flourished in the reign of the Norman Edwards, and died A.D. 1349, tells a story of a witch who was attempting to impose on the simple people of the time. It was a fine summer’s night, and the Moon was suddenly eclipsed. ‘Make me good amends,’ said she, ‘for old wrongs, or I will bid the Sun also to withdraw his light from you.’ Bradwardine, who had studied with Arabian astronomers, was more than a match for this simple trick, without calling in the aid of the Saxon law. ‘Tell me’, he said, ‘at what time you will do this, and we will believe you; or if you will not tell me I will tell you when the Sun or the Moon will next be darkened, in what part of their orb the darkness will begin, how far it will spread, and how long it will continue.’

The story itself illustrates the fact that “simple people of the time” continued to believe that eclipses were supernatural phenomena, and the Website above, in its accounts of medieval eclipses (Famous Eclipses of the Middle Ages – Part One and Part Two) describes several incidents in which eclipses were interpreted by common folk – and even by kings, until the twelfth century – as bad omens. (In some cases, eclipses even caused kings to drop dead of shock.)

The point I wish to make, however, is that the decline in supernatural interpretations of eclipses was already well under way by the late Middle Ages, and that it was caused by the proliferation of medieval astronomy, which the Church took an active role in promoting, after acquiring from the Arabs the skills required to predict the movements of the celestial bodies with a high degree of accuracy.



The upshot of this investigation is that those authors who interpret Jean Buridan, Nicolas Oresme, St. Albert the Great and St. Thomas Aquinas as espousing a form of methodological naturalism have misread their writings: all we can say is that these medieval philosophers viewed the scope of science in Aristotelian terms, and for that reason, they excluded singular phenomena – and, in the case of St. Albert, transcendent Being as well – from its scope. In so doing, they were, as I argued, placing an unduly narrow restriction on the scope of scientific inquiry. Nevertheless, they all believed in the legitimacy of investigating alleged miracles, and they also believed that miracles sometimes happen. They also believed that intelligent agents could act on heavenly bodies, through the sheer force of their intellects.

Finally, I exploded the myth, still propagated in some quarters, that the Middle Ages was a deeply superstitious era, in which even learned people ascribed phenomena such as epidemics, earthquakes and eclipses to acts of God – or the Devil. The evidence shows that on the contrary, scientists and doctors were well aware that these events were natural phenomena.

4 Replies to “Exposing the Hoary History of Methodological Naturalism: Does it really go back to the Middle Ages?

  1. 1
    Mapou says:

    Medieval thinkers may not have believed in naturalism but the idea of evolution is much older than the middle ages. It started way back in the 4th century B.C. with Greek philosopher Empedocles’ theory of evolution by trial and error. It may even be older than this. Many ancients believed in the spontaneous appearance of life from dirt.

  2. 2
    Mung says:

    Thanks vjt.

    It would seem that the medieval scholastics had an entirely different conception of science than we do today. It would be an anachronism to force our concept of science on to their statements as if it could somehow demonstrate that they were methodological naturalists.

    An Introduction to Scholastic Philosophy

    The Emergence of a Scientific Culture: Science and the Shaping of Modernity 1210-1685

  3. 3
    jimmontg says:

    Some scientists still believe that life came from clay crystals as proteins from amino acids formed on it’s matrix as it hardened to more complex grids. It is well known that without a protective membrane proteins could never form underwater. OOL researchers still have absolutely no idea how a chain of amino acids becomes a protein. They still believe life comes from dirt.

    I mostly studied Medieval thought on theology and against Epicurean materialism that came through the poems of Lucretius. It was a long time ago, but when I first saw it I really didn’t catch the similarity to Darwin’s thoughts on the matter. On The Nature Of Things the ancient anthem of materialism and denial of God or gods. The cause of all things by natural laws and chance.
    A philosophy in search of evidence. If you are looking for the beginning of Darwinist thought and where it came from look no further than here in the works of Titus Lucretius Cara.

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    StephenB says:

    VJ, you have provided a splendid commentary on a vitally important subject. Indeed, there was no such thing as “methodological naturalism” until late into the 20th century. Ronald Numbers has been skewing the analysis (misrepresenting the facts?) for years.

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