The following is a lecture delivered to the Hillsdale Catholic Society, at Hillsdale College, MI, 11 April 2018. I would like to thank Dr. Jeffrey Lehman and Samuel Roberts of the Catholic Society for their hospitality on campus, and The Catholic House off-campus for providing me with accommodations during my stay. The lecture was preceded by a seminar on Charles De Koninck’s “Introduction to the Study of the Soul,” and I would like to thank the attendees of that seminar for a wonderful discussion, especially our seminar hosts Peter Cross and Colin Brown. The lecture itself is based on ideas that De Koninck develops in that essay of his on the soul, which is available in the original French here. An English translation should soon be available from the Charles De Koninck Project. The appendix to the text below is my translation of St. Thomas’s prooemium to his commentary on Aristotle’s De Caelo. Throughout the text of the lecture itself, the prooemium is quoted in boldfaced type.
St. Thomas Paving the Way for Cosmology
by John G. Brungardt
Lecture at Hillsdale College, Hillsdale, MI1
Imagine that you are a student at an ancient monastery near a flourishing university town in the early modern age, say around 1645. The university is already old, of medieval origins, but it is young compared to the venerable monastery, whose massive library is even more renowned. You had been for several years the disciple of a great master of theology and philosophy, a Dominican. However, he has recently passed on to his eternal reward—Deo volente—and as such you now oversee the final edition and publication of his philosophical magnum opus. For months you have carefully reviewed his manuscripts, preparing them to be sent to a printing house in Rome, after due approval is received from the master general of the Dominican Order. Yet one night, you are awakened to alarms. You look outside your cell to see the library engulfed in flames. “At least my master’s manuscripts are safe here in my cell!” is your first thought—you will mourn later over the irreplaceable treasures now lost in the great library. Nonetheless, you turn in a fit of nervousness to your desk, and count the tomes. Yes, here is the treatise on metaphysics, and logic, and natural philosophy, on generation and corruption, and the treatise on the soul, all following the Philosopher’s texts and the Angelic Doctor’s exposition. Then you stomach sinks: Where is your master’s treatise on the heavens, on the De Caelo?
If you have read Umberto Eco’s The Name of the Rose, you might have a penchant for attributing lost medieval manuscripts to library fires. That is what I did while trying to determine the reasons behind the missing treatise on De Caelo that failed to sally forth from the pen of the great Thomistic commentator John Poinsot, or, John of St. Thomas (1589–1644). Surely only fire and great misfortune could account for the incomplete status of his great Cursus Philosophicus: one finds in it all parts of speculative philosophy save a treatise on Aristotle’s De Caelo. John was a contemporary of Descartes and Galileo as well as a formative influence on 20th century Thomists such as Jacques Maritain and Charles De Koninck. Nonetheless, John voluntarily withheld that portion of his Cursus Philosophicus dealing with the De Caelo. As one scholar notes, this “handling of the traditional philosophy of nature is revolutionary in a negative way, by deletion.”2 Furthermore, this deletion or possible self-censorship occurred in 1634, which was not only “the year of the famous condemnation in Rome of Galileo” but “also the year in which the traditional treatment of astronomy . . . was tentatively adjudged irrelevant to the essential principles and proper understanding of the Aristotelian philosophy of nature by the professor principally charged at that time with the development of the curriculum of Arts”3 at the University of Alcalá, where John Poinsot taught.
It seems that Thomistic cosmology never recovered after this deletion. Indeed, Thomists as late as Salvatore Roselli—whose Summa philosohica of 1777 was reprinted for 60 years (as late as 1837)—propounded that the heliocentric theory of Copernicus was acceptable only as a “hypothesis” and not as a “thesis.”4 Even today, on the one hand, the scholar Thomas Litt maintains that basic principles of Thomistic metaphysics are in great trouble without the existence of the celestial spheres, whose efficient causality provided hierarchical order and integrity to the physical cosmos.5 On the other hand, the physicist, theologian, and philosopher-historian of science Stanley Jaki castigated Thomists in 1989 for not having made use of those same resources to propose a coherent Thomistic philosophical account of Big Bang cosmology.6 What might have been a wise silence on the part of John of St. Thomas is a silence that has not been filled during the intervening four centuries with a new Thomistic cosmology.
In this paper, I will only outline what this new effort should look like. One of my teachers once remarked that modern cosmologists are in a position to finally carry out the project of the study of the universe which St. Thomas outlines in his introduction, or prooemium, to Aristotle’s De Caelo. This observation struck me as something that was intuitively true but difficult to work out in detail. In the following I begin to work out this claim. First, I consider St. Thomas’s prooemium to his commentary on Aristotle’s De Caelo and then briefly compare the structure of the project Aquinas describes with the results of modern cosmology (what scientists today would call the standard or concordance model). In this way, we can begin to recover what St. Thomas thought it meant to approach the study of the universe in a fully philosophical and scientific way, and then begin to see if his principles have a sufficiently powerful plasticity along with their perennial staying power so as to be able to incorporate new insights from our inquiry into the physical universe.7
2. St. Thomas and the prooemium to his commentary on Aristotle’s De Caelo
St. Thomas’s prooemium is divided into five paragraphs in the Leonine edition; in nn. 1–3 he compares cosmology with the natural sciences as a whole; in nn. 4–5 he defines what cosmology studies primarily, the universe. He opens in [n. 1] by reminding us of what Aristotle says in Physics Book I, Chapter 1, regarding the mission of scientific inquiry: “We think that we know each thing when we know the first causes, and the first principles, all the way to the elements.” If this is supposed to remind us of the mission of natural philosophy, I think St. Thomas also means to remind us of Aristotle’s second point in that chapter of the Physics, namely, how this is to be accomplished.
This how or the method consists in proceeding from what is more known to us to what is more known “by nature.” This requires that our inquiries proceed from general and indistinct thoughts about the world to more specific and clearly defined thoughts about the world. Natural philosophers, trying to figure out the whole universe and all of its contents, act like children who name the parts and properties of nature in confusion before knowing the truth about nature distinctly. (Recall that Newton compared himself to a child playing in front of an unknown ocean of truth.)
This point about the order in our knowledge, as opposed to the order in nature, is important, since Aquinas goes on to note that the primary mission of natural philosophy clearly shows that there is an ordered progression in the sciences, as they proceed from the first causes and principles all the way to the proximate causes, which are the elements constituting the essence of a thing. (So, note here that “elements” does not mean the chemical elements.) However, this “progression in the sciences” is a double progression. We can progress in our own knowledge and we can progress according to how things are. That is, the order of our discovery differs from the order of causality in things. What I am trying to draw out is that St. Thomas must have both of these orders in mind, even though he is speaking expressly about the order of being and causality in things. He continues, saying that the progression of the sciences is a work of reason, whose proper work is to order.Whence in all works of reason some order is found, insofar as reason proceeds from one thing to another. But again, reason can progress from one thing to another in at least two ways: from what is better known to us at first, or from what is better known or more a cause in things themselves. We must keep in mind this two-fold progression in the sciences: from what is first quoad nos and from what is first quoad se.
In order to specify how reason makes progress in the sciences, St. Thomas next considers a clearer case, namely the progression in practical reason (whose consideration concerns those things which we do) with the hope that similar features will show up in speculative reason (whose consideration concerns those things made by something other than ourselves). Now, one finds a fourfold order in the consideration of practical reason according to the prior and the posterior. As we walk through each of these four aspects, note where the analogy limps, as St. Thomas has already pointed out: the practical order concerns things we humans do or make, while speculative reason considers those things not made or done by human beings, that is, those things made “by nature”.8The practical side of the analogy begins in [n.2].  First, there is [an order of consideration] according to the order of apprehension, insofar as the builder first apprehends the form of the house absolutely and afterwards induces it into matter. Now, this “absolutely” is a bit disconcerting. Perhaps we can understand it using a comparison to architects and engineers. An architect could conceive of a new design for a house “absolutely” or “apart from” its material conditions (when, where, and with what exactly the plan for the house will be realized). This is also what people do if they design their “dream home.” It has all the features of a real physical house, just sans a physical location and plans-in-execution.
Let us skip ahead to see how St. Thomas compares this order of apprehension to speculative reason later on in [n.2]: [1´] The first order is the order according to which [speculative reason] proceeds from what is more common to what is less common. And this order answers analogously to the first order [in practical reason] which we called [the order of] apprehension. For universals are considered according to an absolute form, while particulars are considered according to an application of form to matter, just as the Philosopher says in De Caelo Book I that those who speak of “heaven” speak of the form, but those who speak of “this heaven” speak of form in matter. Now, recall the dream house. It is something that is possible for us to do or make, or, at least, it’s possible in principle. In the speculative order, where the example is “the heaven” or “the universe,” we can see where the analogy limps. In speculative thinking, we’re not considering something absolutely that is a “dream” or “unreal” or not yet existing, but something that is real (in this case, the universe). However, we consider it “absolutely” or “abstractly,” that is, in its conceptual generality. The progression in this line of thinking therefore goes from the more general to the more particular, indeed, from general ideas to particular applications. St. Thomas frequently speaks about this when comparing general ideas and arguments in Aristotle’s Physics to how they can be applied to particular, concrete natures.
Let us now consider the second order:  Second, there is [an order of consideration] according to the order of intention, according to which the builder intends to complete the entire house, and because of this he does what work soever on the parts of the house. Let us return to our comparison above between the architect and the engineer. The first stage, the order of apprehension, belongs to the architect; stage two belongs to the engineer (or foreman). So, in moving from the first stage to the second, we move from abstractly considered shape and lines and the general layout, flow, and aesthetic of the house to its practicable realizability. Yet in our practical thought we are still only thinking about the house. The architect wants flying lines and a soaring design; the engineer figures out how to make it possible, and in what order we will need to proceed so as to actually build the house. So, this order of thinking involves a myriad of practical details, which complexity is important for the comparison to speculative reasoning.
What order corresponds to this second stage in speculative reasoning? In thinking something out theoretically, [2´] the second order is the order according to which [speculative reason] proceeds from the whole to the parts. Now, for the sake of clarity, let us call this order a process of analysis, taking a whole apart or “analyzing” it in our thinking. But of what sort is this analysis? And how does it compare to the practical order of intention? St. Thomas explains that this order answers analogously to the order [in practical reason] that we called [the order of] intention, namely, as the whole is prior in consideration to the parts—not any parts whatsoever, but the parts which are material parts and which are individuals, like the semicircle, in whose definition the circle is placed (for a semicircle is the half part of a circle), and the acute angle, in whose definition the right angle is placed (for an acute angle is an angle less than a right angle). What does this mean?
To understand this, we need to grasp the difference between material parts and formal parts. We’re discussing a “whole” in a conceptual way: “house,” or “circle,” or “right angle.” Let us consider the definition of circle: “A circle is a plane figure contained by a single line [which is called a circumference], (such that) all of the straight-lines radiating towards [the circumference] from one point amongst those lying inside the figure are equal to one another.”9 Now, all of the ideas that we need to understand this definition (e.g., plane, figure, line, straight line, point, equality, inside, outside) are the formal parts of the definition. The formal parts of a concept are those parts without which we cannot understand the whole idea. By contrast, a material part is not needed to understand the whole. Rather, the whole (and implicitly) its formal parts are needed to understand any material part. Thus, the semi-circle is defined in terms of a circle. Note how St. Thomas says that there are also material parts which are individuals: that is, it accrues to circle and to right angle to be divided thus; whence, these divisions are not parts of their species. That is, a division here in this way with this diameter (making a particular semi-circle) is one of infinitely many ways of dividing the same circle. Thus, even more strongly, we can say that knowing the material parts (since they are potentially infinite) are not the parts needed to understand some whole, rather, we need formal parts, for these latter types of parts [parts of species] come prior in consideration to the whole, just as flesh and bones in the definition of man . . . .
Now, it is interesting to consider, for a moment, whether we first come to know the material parts or formal parts of a whole. To take the example of the type of flesh and bones in a human being, this requires detailed investigation; ultimately, this is to ask about specifically human organs, proteins, DNA, etc. The formal parts are not known or obvious to us at first, but to the degree that they are known the whole is known. Therefore, we must proceed analytically and by induction, investigating many individual cases (and by implication what will involve material parts) before explaining a given whole. Thus, before the formal parts are known, the whole is known vaguely. Consider also the circle: we at first discover what it means to be plane, figure, line, straight line, point, equality, inside, outside, etc., but only when we properly order all of these concepts as parts into the whole notion of a circle do we achieve insight into what the circle is. So, I propose that this second stage implicitly contains two kinds of analysis. It includes the analysis of the whole in terms of both its formal and its material parts.
Now for the third order:  Third, there is [an order of consideration] according to the order of composition, insofar as [the builder], of course, first hews the stones and afterwards constructs one wall with them. Note that here we move from the order of practical thought to an order in reality. We were previously planning out (in our intentions) how to make the house. To what does this correspond in the speculative order? The Angelic Doctors states: [3´] Now, the third order is the order according to which [speculative reason] proceeds from simple things to composed things, insofar as composed things are known through simple things as through their principles.
Even from the description regarding the speculative order, it seems clear that the progress is from simpler wholes to more complex wholes that actually exist. So, we are no longer speaking about a conceptual analysis but something involving synthesis and explanation of posterior beings by prior beings. This makes sense if we recall the general mission statement of natural philosophy: “We think that we know each thing when we know the first causes, and the first principles, all the way to the elements.” Our goal is only attained once we reach the specific elements of each kind of thing. Now, depending upon what we are studying, these “elements” will be different. The word “element” does not mean only chemical elements, but rather the formal parts of a whole. The third stage is where we use the formal parts that define certain wholes, which wholes are in turn simple in comparison to other compound things. St. Thomas is being rather general here. Does this composition occur within the progression of one science alone (e.g., in chemistry, which considers the chemical elements before compounds; or in biology, which considers the cell before systems or organs)? Or does this progression in composition even take place between different sciences? At the very least, this order of composition is a type of conceptual synthesis that tracks how things are composed in reality.
Now for the final order of consideration, which is  . . . according to the order of sustaining the artifice, as when the builder first lays the foundation upon which the other parts of the house are sustained. This adds specificity to the previous practical order of composition. Stages three and four are not separate in time. Rather, the focus in stage four is on the fact that some parts of the composed whole are more important than others for the existence and being of the whole. Speculatively: [4´] The fourth order is the order according to which the principal parts must be considered beforehand, as the heart and liver before the arteries and blood. So, speculatively, this final order adds the idea that we are not merely considering the real definitions of things, their formal parts, or the simple and complex wholes, but also the relative importance of certain parts in the whole. We have not only composition but hierarchy as well.
Now it remains to see how these four orders in speculative consideration (apprehension, intention, composition, and sustaining) apply to cosmology. St. Thomas does this in [n. 3] The first order, of apprehension, determines about the common things of nature in the book of the Physics, in which the mobile insofar as it is mobile is treated. Whence it remains in the other books of natural science to apply these common things to the proper subjects. That is, instead of talking about changing things or motion or place or time or moving causes in general, the natural philosopher must take these general ideas about things based upon common experience and apply them more and more specifically to concrete natures. This requires the use of more and more specialized experience.10 This shift between what our ordinary experience allows us to know about nature and the specialized, experimental evidence needed for this “application” is very difficult to achieve; it is indeed monumental, as the history of the natural sciences bears witness.
Now, for reasons that we can’t go into here, Aristotle’s Physics shows that nothing moves except the extended [body]; consequently, all particular natural sciences will study bodies in various ways. So, St. Thomas concludes, it is in bodies one should attend to the three other orders. First, [2´´] insofar as the whole corporeal universe is prior in consideration to its parts. Now, if we recall our discussion above, this means that the whole corporeal universe is prior in consideration to its material parts, namely, the parts within it that are at least in some way defined by the formal parts of the corporeal universe (whatever those are), as well as individual material objects. Next, bodies are considered [3´´] in another way, insofar as simple bodies are prior in consideration to mixed bodies. This aligns with our discussion above of the synthetic order of consideration. We should start thinking about what this involves in a modern cosmology. Perhaps the basic elements before stars and planets, and stars and planets before galaxies. But what about more complex chemical compounds? What about living things? Before I offer some ideas, let us consider the final order. St. Thomas says, lastly, [4´´] . . . that bodies are considered insofar as among simple bodies it is necessary to first consider the prior [bodies], namely the heavenly body, through which all other bodies are supported. Now, we recognize in this assertion the hierarchical order between the parts of a whole. It seems immediately more difficult to apply this to modern cosmology, and indeed the non-existence of the heavenly spheres, as we mentioned, is the source of scholastic troubles to begin with. But now that we have finished the heart of St. Thomas’ prooemium to cosmology, we can note in summary that he considers it to be a natural prolongation of what one would study generally in Aristotle’s Physics. We take our general ideas of motion, causality, and body which we draw from common experience and then make them more specific using specialized experience. In cosmology, this leads us to study the whole-part composition of the universe, its complexity at various scales, and the hierarchical order of its parts.
3. St. Thomas and the proper subject matter of cosmology
Before we can consider whether this overall project that St. Thomas outlines is applicable to the cosmology of today, we must consider what St. Thomas thinks that the subject of the De Caelo actually is. There is actually a debate about this that he deals with in [nn. 4-5]. The first position comes from Alexander of Aphrodisias. “Alexander was of the opinion that the principal subject treated in the book is the universe itself.” This is the position that St. Thomas will eventually side with, qualifiedly. Alexander’s position “assumes that [Aristotle’s De Caelo] determines certain things pertaining to the whole universe, namely that it is finite, that there is only one [universe], and other things of this sort.” This is a classic Aristotelian procedure: a science studies its subject’s properties. (As an aside, that this also requires knowledge that the subject of the science exists and what that subject is must be assumed by the science. Thus, cosmology assumes both that and what the universe is, at least in some way. So, what science or part of philosophy proves or defends or shows us the existence and definition of the universe? It cannot be cosmology!)
The second position is taken by Iamblichus and Syrianus. According to them, “the principal subject aimed at by this book is the circularly moving heavenly body, and because of this it is titled On the Heaven.” However, St. Thomas argues that this is insufficient, because then the book would only consider other sorts of body either as a consequence . . . , or incidentally . . . .” That is, the second view requires that the other four elements of earth, air, water, and fire are not essential or formal parts of the universe. St. Thomas does not think this is plausible, for Aristotle devotes half of the treatise (Books III and IV) to considering these simple bodies “as if part of his principal aim.”
The third position belongs to Simplicius: “It seemed to others, as Simplicius says, that the intention of the Philosopher in this book is to determine things about the simple bodies, insofar as they share in the common intention of simple bodies.” Thus, Simplicius thinks that Alexander’s position is too much: if you say that this book is about the universe, then you have to consider everything in the universe, even living things or human beings. But Aristotle obviously does that in other books. So, Simplicius tries to be more precise and say that cosmology studies those bodies that principally compose the universe, namely, the elemental simple bodies. Recalling our discussion of formal parts, this sounds promising. However, St. Thomas turns Simplicius’s argument against him. If the De Caelo were about the simple bodies as such, then Aristotle should not leave out a consideration of what we would call the chemical powers of the elements. But he does leave that out; he only considers the elemental bodies as “to their lightness and heaviness.” What exactly this specification implies we will consider in just a moment.
In review: position (b) thinks that cosmology should consider one principal type of body in the universe as such, and all the others derivatively or incidentally. However, this would mean that we are really considering the universe incidentally, which is bad for the science of the universe to do. Also, position (c), Simplicius’s position, thinks that cosmology studies the simple or elemental bodies as such. However, this would also mean that we are considering the universe only incidentally or “by the way.”
For such reasons, St. Thomas maintains in [n.5] that the opinion of Alexander seems more reasonable, that the subject of this book is the universe itself, which is called the heaven or the world. And the simple bodies are considered in this book insofar as they are parts of the universe. That is, the universe is essentially the subject of the treatise, not incidentally. If this is the case, St. Thomas needs to tell us, at least in outline, what makes for the essence of the universe. And he does so: the corporeal universe is constituted from its parts according to an order of position. Thus, this book considers only those parts of the universe which first and per se have position in the universe, namely the simple bodies. Now, by “position” or “situs” here, St. Thomas does not mean the place of bodies.11 Rather, position is the order that obtains between all bodies overall with respect to their places. Of course, this implies the natural places of all bodies in the whole universe. Here, St. Thomas arrives at the qualification to Alexander’s position that allows him to avoid the objection that crippled Simplicius. The simple bodies are not considered as such but only as parts within the universe as a whole. This means parts according to natural positions, for the corporeal universe is defined by such an order of position, so its formal parts are these kinds of body which first and per se (or of their very nature) have such position.
Indeed, St. Thomas makes two further exclusions, in the areas of what we could call chemistry and biology: Whence also the four elements are not considered in this book insofar as they are hot or cold, or the like, but only insofar as they are heavy and light, from which their position in the universe is determined. That is, we first exclude chemical properties and their results (reactions and compounds). (This does not mean that cosmology could not make use of chemistry, but rather than cosmology is not chemistry, a satisfying result.) St. Thomas continues: The other parts of the universe, such as stones, plants, and animals, are not determined in position according to themselves, but according to the simple bodies, and thus they are not considered in this book. We would say nowadays that inorganic and organic chemistry as well as biology are not properly parts of cosmology. The universe contains complex chemicals and living things, but the study of the physical universe as such does not concern them. Complex chemicals and living things would thus be material parts and not formal parts of the physical universe, insofar as cosmology is concerned. St. Thomas closes with a customary move that shows how his qualification of one authority (Alexander) fits with other authorities, for his position resonates with what is customarily said among the Latins, that this book considers body mobile as to position, or according to place, which [type of] motion is indeed common to all the parts of the universe.
4. Conclusion: the science of cosmology today
Now, by way of conclusion, I would like to point out the clearest ways in which Thomists today could begin to make use of the big picture that St. Thomas outlined. That is, how can Thomists make use of the discoveries of modern cosmology and integrate them into a broader philosophical vision for cosmology? Can modern cosmology “complete the entire house” now that the historical progression of science has reached its current state? I end with three points.
First, let’s note something concerning the jump from the first order to the final three orders. St. Thomas himself sets the first order (apprehension) apart from the final three (intention, composition, and sustaining), and it bears knowing why he did so. The reason is not that the first order is philosophy and that the other three are the sciences (although, that is the case if one looks at a university course catalog). Rather, the first order is fueled by common, general experience and the last three involve particular, specialized experience.
Now, we frequently hear about this difference as the founding insight of modern science: the use of experiment and measurement. Yet it bears reflecting on just how difficult this transition is; we can do so by way of a quotation from Wittgenstein. One of his students writes that “[Wittgenstein] once greeted me with the question: ‘Why do people say that it was natural to think that the sun went round the earth rather than that the earth turned on its axis?’ I replied: ‘I suppose, because it looked as if the sun went round the earth.’ ‘Well,’ he asked, ‘what would it have looked like if it had looked as if the earth turned on its axis?’”12 The point is that it would have “looked” just the same. Thus, the development of a specific enough physics for understanding the heavens did not merely have to improve our sense of sight but rather nuance our interpretation of our sense of touch and with it our sensations of motion (pushing and pulling, moving and being moved). Indeed, many of the arguments against the motion of the earth were based upon such sensations of what rapid motion (or more precisely, acceleration) was supposed to feel like. Both Galileo and Einstein proposed thought experiments to have us carefully dissociate our felt sensation of motion and being moved, on the one hand, from the principles at work in inertial and gravitating bodies, on the other. Other discoveries in modern astronomy show how long and difficult is the necessary transition from common experience to the scientific experience: principally, I think of discovering the finitude of the velocity of light and the discovery of the spectra of different types of materials and their spectral shifts, red- or blueshifts, which allowed scientists to infer the universe-wide expansion. It is hard for reason to convince our senses just how much the immediately sensible does not also immediately reveal the essences or natures of things.
Now, another point we can make is that St. Thomas’s own definition of the subject of cosmology (the material universe) must be modified. Instead of saying that cosmology studies the corporeal universe, “[which] is constituted from its parts according to an order of position,” we should specify “according to an order of position in both place and time.” That is, modern cosmologists have discovered how essential historical development is to the cosmos as a whole. The typical example here is that only certain elements can form during the Big Bang era of the universe (H, He, Li), while the heavier elements, especially those required for life, can only be formed in stars. So, the very existence of heavier elements such as carbon entails a historical order of development at the scale of the whole universe. So, the history of the parts of the universe and their positions within the universe is not incidental to it as a whole.
A last point that I would like to make is that modern cosmology still follows the last three orders of speculative consideration outlined by St. Thomas. That is, modern cosmology still studies the whole-part composition of the universe, its complexity at various scales, and the hierarchical order of its parts. Advances in exploring the material parts of the universe can be seen by considering recent maps of the universe at the scale of superclusters. Yet cosmological models also provide us with some insight into the formal parts of the universe as a whole, especially how it behaves with regard to spatio-temporal positions. Natural constants such as the gravitational constant (the cosmic-scale attractive force) or the cosmological constant (the cosmic repulsive force) are essential to modern cosmology’s understanding of the universe as a whole. So, such constants are akin to the formal parts of the universe insofar as they signify principles essential to its being and behavior. The order of complexity I have already mentioned with regard to nucleosynthesis. This complexity is also a necessary condition for life in the cosmos, thus showing an order between wholes and parts in the cosmos and wholes and parts in biospheres. Lastly, the cosmos is also studied with respect to its fundamental parts. This is a more controversial guess, but it seems that modern cosmology still has to maintain that space itself, insofar as physical space is capable of expansion, possesses some type of cosmic-scale behavior, agency, and perhaps even purpose. If some of these guesses could be fleshed out in more detail, then perhaps someday someone will be able to write that missing De Caelo treatise for John Poinsot, even if, by the exigencies of history and discovery, it was only 400 years in the making.
Appendix: St. Thomas, In Libros Aristotelis De Caelo et Mundo Expositio, Prooemium
[1.] As the Philosopher says in Physics Book I, “We think that we know each thing when we know the first causes, and the first principles, all the way to the elements.” From this the Philosopher clearly shows that there is an ordered progression in the sciences, as they proceed from the first causes and principles all the way to the proximate causes, which are the elements constituting the essence of a thing. And this is reasonable, for the progression [processus] of the sciences is a work of reason, whose proper work is to order. Whence in all works of reason some order is found, insofar as reason proceeds from one thing to another. And this is clearly the case in both practical reason (whose consideration concerns those things which we do) as well as in speculative reason (whose consideration concerns those things made by something other than ourselves).
[2.] However, one finds a fourfold order in the consideration of practical reason according to the prior and the posterior.
 First, there is [an order of consideration] according to the order of apprehension, insofar as the builder first apprehends the form of the house absolutely and afterwards induces it into matter.
 Second, there is [an order of consideration] according to the order of intention, according to which the builder intends to complete the entire house, and because of this he does what work soever on the parts of the house.
 Third, there is [an order of consideration] according to the order of composition, insofar as he, of course, first hews the stones and afterwards constructs one wall with them.
 Fourth, there is [an order of consideration] according to the order of sustaining the artifice, as when the builder first lays the foundation upon which the other parts of the house are sustained.
Likewise, there is also a fourfold order in the consideration of speculative reason.
[1´] The first order is the order according to which [speculative reason] proceeds from what is more common to what is less common. And this order answers analogously to the first order [in practical reason] which we called [the order of] apprehension. For universals are considered according to an absolute form, while particulars are considered according to an application of form to matter, just as the Philosopher says in De Caelo Book I that those who speak of “heaven” speak of the form, but those who speak of “this heaven” speak of form in matter.
[2´] The second order is the order according to which [speculative reason] proceeds from the whole to the parts. And this order answers analogously to the order [in practical reason] that we called [the order of] intention, namely, as the whole is prior in consideration to the parts—not any parts whatsoever, but the parts which are material parts and which are individuals, like the semicircle, in whose definition the circle is placed (for a semicircle is the half part of a circle), and the acute angle, in whose definition the right angle is placed (for an acute angle is an angle less than a right angle). However, it accrues to circle and to right angle to be divided thus; whence, these divisions are not parts of their species. For these latter types of parts come prior in consideration to the whole, just as flesh and bones in the definition of man, as is said in Metaphysics Book VII.
[3´] Now, the third order is the order according to which [speculative reason] proceeds from simple things to composed things, insofar as composed things are known through simple things as through their principles. And this order is likened to the third order [in practical reason] which we called [the order of] composition.
[4´] The fourth order is the order according to which the principal parts must be considered beforehand, as the heart and liver before the arteries and blood. And this is analogous to the practical order [of sustaining the artifice], according to which the foundation is laid beforehand.
[3.] And this fourfold order is considered in the process of natural science.
[1´´] For first one determines about the common things of nature in the book of the Physics, in which the mobile insofar as it is mobile is treated. Whence it remains in the other books of natural science to apply these common things to the proper subjects. The subject of motion, however, is magnitude and body, because nothing moves except the extended [body].
Now, in bodies one should attend to the three other orders.
[2´´] In one way, insofar as the whole corporeal universe is prior in consideration to its parts;
[3´´] in another way, insofar as simple bodies are prior in consideration to mixed bodies;
[4´´] and in a third way, insofar as among simple bodies it is necessary to first consider the prior [bodies], namely the heavenly body, through which all other bodies are supported.
And these three are treated in this book, which among the Greeks is called On the Heaven. For in this book are related [2´´] certain things pertaining to the whole universe, as is clear in Book I, [4´´] certain things pertaining to the heavenly body, as is clear from Book II, and [3´´] certain things pertaining to the simple bodies, as is clear from Books III and IV. And thus this book comes with some reason after the book of the Physics. Because of this, body is immediately considered at the beginning of this book, to which it is necessary to apply all those things which were related about motion in the book of the Physics.
[4.] Accordingly, because diverse things are related in this book, there was a doubt among the ancient commentators on Aristotle concerning the subject of this book.
(a) For Alexander was of the opinion that the principal subject treated in the book is the universe itself. Whence, since “heaven” is said in three ways (sometimes it means the last sphere itself, sometimes the entire circularly moving body, and sometimes the universe itself), he claims that this book is titled On the Heaven meaning On the Universe or On the World. By making this assertion he assumes that the Philosopher in this book determines certain things pertaining to the whole universe, namely that it is finite, that there is only one [universe], and other things of this sort.
(b) On the contrary, it seems to others that the principal subject aimed at by this book is the circularly moving heavenly body, and because of this it is titled On the Heaven. Now, the books considers other sorts of body either as a consequence (insofar as they are contained by the heaven and receive its influence, as Iamblichus says), or incidentally (insofar as notice is taken of the other bodies so as to manifest the things which are said about the heaven, as Syrianus says). But this does not seem probable, because after the Philosopher considers the heaven in Book II, in Books III and IV he adds a consideration of the other simple bodies as if part of his principal aim. For it is not the custom of the Philosopher to assign a principal part of some science to things which are taken incidentally.
(c) And therefore it seemed to others, as Simplicius says, that the intention of the Philosopher in this book is to determine things about the simple bodies, insofar as they share in the common intention of simple bodies. And because the heaven is the principal body among the simple ones, upon which the others depend, the whole book is named after the heaven. And, as he says, it is no objection that certain things pertaining to the whole universe are considered in the book, because such conditions accrue to the universe insofar as they accrue to the heavenly body, namely to be finite and eternal, and other such things. However, if the principal intention of the Philosopher were to determine about the universe, or the world, it would be necessary that Aristotle extend his consideration to all the parts of the world, even to the plants and animals, as does Plato in the Timaeus. Yet the very same reasoning could be used to argue against Simplicius: because if the principal aim of the book were the simple bodies, it would be necessary that all those things which pertain to the simple bodies be treated in this book. However, only those things which pertain to their lightness and heaviness are related here in this book, while the rest are related in On Generation.
[5.] Thus, the opinion of Alexander seems more reasonable, that the subject of this book is the universe itself, which is called the heaven or the world. And the simple bodies bodies are considered in this book insofar as they are parts of the universe. However, the corporeal universe is constituted from its parts according to an order of position [secundum ordinem situs]. Thus, this book considers only those parts of the universe which first and per se have position in the universe, namely the simple bodies. Whence also the four elements are not considered in this book insofar as they are hot or cold, or the like, but only insofar as they are heavy and light, from which their position in the universe is determined. The other parts of the universe, such as stones, plants, and animals, are not determined in position according to themselves, but according to the simple bodies, and thus they are not considered in this book. And this resonates with what is customarily said among the Latins, that this book considers body mobile as to position, or according to place, which [type of] motion is indeed common to all the parts of the universe.
1 This presentation was produced as part of my postdoctoral research project. FONDECYT POSTDOCTORADO, Proj. No. 3170446.
2 John Deely, “Editorial Afterword,” in John Poinsot, Tractatus de Signis: The Semiotic of John Poinsot, ed. by John Deely (Berkeley: University of California Press, 1985) 404.
3 Ibid., 403.
4 See Salvatori Rosellius, Summa philosophica t. 3 (Matriti: Typis Benedicti Cano, 1788) 184–206. it should be borne in mind that Roselli features detailed citations not only of Newton’s Principia but also of the empirical observations grounding that work, e.g., Roemer’s discovery of the finitude of the velocity of light based upon observations of the moons of Jupiter.
5 Thomas Litt, Les corps célestes dans l’univers de Saint Thomas d’Aquin, Vol. VII. Philosophes Médiévaux (Louvain/Paris: Publications Universitaires/Béatrice-Nauwelaerts, 1963).
6 See Stanley L. Jaki, “Thomas and the Universe,” The Thomist: A Speculative Quarterly Review 53.4 (1989): 545–72.
7 See Petrus Hoenen, Cosmologia, 5th ed. (Roma: Universitas Gregoriana, 1956) v–vi; Hoenen notes that his goal is to specify the general metaphysical principles to be found in Thomism. The problem seems to be that the peripatetic general principles will collapse because they cannot be specified, just as the mechanists’ metaphysical principles fell. Yet he maintains this is not the case: the “plasticity of the peripatetic principles” is admirable, if only we follow out a critical method of engaging the sciences.
8 The great ethical drama of modern science and its technological fruits is the apparently indefinitely mutable character of this dichotomy, viz., those things subject to human power and those things not so subjected.
9 Euclid, Elements, I, Def. 15 (Fitzpatrick translation).
10 John Deely names this distinction in modes of experience the difference between cenoscopic and ideoscopic knowledge. See Descartes & Poinsot: The Crossroad of Signs and Ideas, Vol. 2 of The Postmodernity and Philosophy Poinsot Trilogy: Contrasting the Way of Signs to the Way of Ideas, Semiotics to Epistemology (Scranton/London: University of Scranton Press, 2008) 3–9, and his Purely Objective Reality (Berlin ; New York: De Gruyter Mouton, 2009) 3–6. He draws the names from C. S. Peirce, who derives them (with changes) from Jeremy Bentham. The Greek roots make the distinction adequately clear for a first understanding: cenoscopic is a commonlook, while ideoscopic is a private look.
11 By “position” or situs here is not meant the order of parts in a whole, but rather the category of situs, for the category implies the notion of place, whereas situs can also mean the order of parts within a whole and thus be a difference in the category of quantity. See St. Thomas, In Phys., lib. IV, lect. 7, n. 4 (Leon.2.167), and compare ibid., lib. III, lect. 5, n. 15 (Leon.2.114). Since place is also in the category of quantity, immobility can be properly added to place, insofar as it implies situs as a species-making difference in quantity as a genus and not a categorical reality.
12 G. E. M. Anscombe, An Introduction to Wittgenstein’s Tractatus, 2nd ed. (1963), ch. 12.