Helene Duhem, in the biography of her father, the famous french physicist, philosopher and historian of science, Pierre Duhem (1861-1916)1, tells us, in a vivid passage, of the excitement her father transmitted when talking about some manuscripts he had recently discovered. It was a common event at the Duhem's when Pierre shared with his daughter the joy he had with one or other scientific result he had proved. This time, however, it was different, for Pierre Duhem was thrilled with some old manuscripts and not with a new physics demonstration. Such a homely event was in due course destined to change the history of science in the twentieth century, and Pierre Duhem's excitement was wholly justified. What the french scientist had discovered were some obscure references to the work of an equally obscure medieval author, Jordanus de Nemore. Following this initial discovery, within a few months Duhem unearthed the work of the great french medieval scholars Jean Buridan and Nicole Oresme, thereby bringing to the surface the impressive and completely ignored continent of medieval physics and cosmology. With an almost unbelievable stamina and dedication Duhem followed the subject to the end of his life, producing, single-handedly, a great number of works of outstanding quality, which culminated in the monumental ten volumes of the Systeme du Monde.2
The history of medieval science was a virtually non-existent discipline until Duhem's works. Furthermore, from its inexistence, historians were more than eager to conclude that the concept itself designated an inexistent chapter of human science: there had been no science in the middle ages. This idea became a standard cliche in the eighteenth and nineteenth centuries, and even today it is from time to time sadly heard in circles of scholars that should know better.
Having set such high standards of scholarship - and one should keep in mind that despite his work in the history of science Duhem always considered himself a theoretical physicist, and a first-rate one he undoubtedly was - Duhem was bound to be followed, in the subsequent decades, by only a handful of brilliant scholars. Anneliese Maier was perhaps the first to truly appreciate the magnitude of Duhem's discoveries and, at the same time, to detect and correct some of his deficiencies. Starting at approximately the same time as Maier's investigations, a series of excellent works appeared, the fruit of a small community of scholars centered in the United States. Historians of science such as Marshall Clagget, Ernest A. Moody, John E. Murdoch, to name but a few, not only have dutifully analized the previous work on their fields, but have on their own brought to light a number of hitherto unknown texts and have in fact re-shaped the modern image of medieval science and in so doing, re-shaped our conceptions of the whole of the intellectual world of the middle ages. This tradition has fortunately extended to our days and has in Professor Edward Grant one of its most distinguished representatives.
Edward Grant had his credits more than established as one of the leading authorities in medieval science studies. In this book, as I will describe below, he adds to his previous works a contribution of exceptional value. For any author addressing the subject of medieval cosmology - Duhem's favorite theme - it is by no means an easy task to produce a work comparable in depth and scholarship to the Systeme du Mondeand furthermore to greatly complete - in extension, but also in rigor - the overall picture of medieval cosmology. And this, I believe, Grant has successfully done.
As the subtitle of this book clearly states, this is a work about cosmological doctrines in a period roughly coincident with the Middle Ages. It is not a book about medieval physics or medieval astronomy. It addresses questions that our "fin-de-siecle" jargon would label as interdisciplinary, but that scholastic authors have treated has a unified corpus of knowledge: questions related to the cosmos as a whole, where strictly philosophical issues are mixed with more scientific concepts. The time span covered in the book - from 1200 to 1687 - if wider than any reasonably limits one might choose for the term Middle Ages, reflects the lifetime of scholastic cosmology. In the author's own words: "Because my objective is to describe and analyze medieval Latin Aristotelian cosmology over the whole of its viable existence, my study begins at approximately 1200 (...) and terminates in 1687 (...)." (p. 9)
Although the book is a superb contribution to the study of cosmology in the period 1200 to 1687, Grant's forte and certainly the part where his contributions are more notorious and where, in a sense, he clearly completes the work of Duhem, is when addressing the later decades, that is, the sixteenth and in particular the seventeenth centuries. In this he is quite consciously advancing in a terra incognita: "Because the final century of Aristotelian cosmology has thus far been virtually ignored, it will form an important aspect of this study, which takes for its objective the whole of late medieval scholastic cosmology" (p.10).
In fact, if medieval science as a whole has been generally neglected in the modern presentations of the history of science, late scholastic thought has been, until today, absolutely forgotten, either by ignorance or, as Grant denounces, by sheer prejudice: "(...) of the 14 authors representing the seventeenth century, only Giovanni Baptista Riccioli, who was an eminent astronomer and physicist, is well known to modern historians of science. (...) The disappearance of these authors from works of modern scholarship may be attributed to a lack of interest in Renaissance Aristotelism, which scholars of the past two centuries have usually portrayed - when they have considered it at all - as a rigid monolithic body of traditional medieval ideas that in the seventeenth century gained notoriety solely for its obstinate opposition to the emerging new science." (pp. 749-750) It is this a priori and monotonous depiction of renaissance Aristotelism which succumbs under the lively descriptions of Edward Grant of the intense debates of seventeenth century scholasticism. One might reasonably claim that the direct contribution of seventeenth century Aristotelism to the appearance of modern science was negligible. From this it does not follow, however, that renaissance Aristotelism was an intellectual corpse simply waiting for disposal. On the contrary, the reaction of late scholastic authors to the irrefutable new observations of Galileo and Tycho Brahe, and to the new conceptual framework of Copernicanism, serves as an example of the reaction of the scientific establishment of all ages. As Grant states, the longevity of Aristotelian cosmology hints to a versatility which is worth understanding: "Perhaps this study will contribute toward that end, so that we may learn, among many other things, why Aristotelian cosmology coexisted with its Copernican rival for at least 144 years (1543 to 1687) before it finally succumbed." (p. 679)
If the importance of a work with such an objective is manifest by itself, the strategy adopted by Grant to achieve its purpose is even more interesting. The whole work revolves around 400 selected questions related to cosmology and drawn from texts of the period considered. These questions are listed in Appendix II (Catalog of Questions) and form the core and the raw material from where stems all the text. The author goes to great lengths in the analysis of the sources since "(...) no study has yet provided us with a detailed description of the nature and sources of medieval cosmology, I have sought to do so in this work" (p. xix).
These questions were drawn from 67 treatises (or 76, depending on the counting of independent works - see the appendices for discussion), the product of the work of 52 authors, starting with Michael Scot (died ca. 1235) and ending with Illuminatus Oddus (died 1683). The amount of information contained in that selection is so large that Grant, after describing the stringencies of the selection procedure, nevertheless acknowledges (p. 765) that not even all questions selected were considered in the main text. In fact, the importance of the Catalog of Questions is so great that, were it not for the gross understatement committed, one could describe the contents of this book as consisting in the identification, selection, and commentary of 400 questions from authors of 1200 to 1687, related to cosmological subjects. Such an achievement would, by itself, be a noble and vast enterprise. The truth is, however, that in the hands of E. Grant, even such a daring objective is transcended into an impressive work, were the author's superb command of the sources is matched by an acute critical insight.
The book starts with an extensive - 59 pages - introduction, divided in three chapters and subtitled: Scope, Sources and Social Context. In these first three chapters the author sets the stage for what will follow. After what has been briefly said above, it is no surprise that the opening pages of this book address the content of Duhem's achievement. In the words of Prof. Grant: "Duhem's contributions to the history of medieval science and cosmology were nothing less than extraordinary" (p.3), but he immediately proceeds to describe the most obvious deficiencies of the work of the french scholar and, more importantly, the aspects in which this work differs from the Systeme du Monde. An important chapter about the sources of medieval cosmology follows, and finally, in chapter 3, Grant analyses the social context in which these works were produced and its possible influence in the development of medieval cosmology. For those readers familiar with Aristotelian physics and cosmology these three introductory chapters form the sufficient background for the book.
After the introductory part, the main text is divided in two parts. Part I: The Cosmos as a Whole and What, if Anything, Lies Beyond; and Part II: The Celestial Region.
Part I (Chapters 4 to 9) analyses questions related to six important topics of discussion of medieval cosmology: Is the world eternal, without beginning or end?; The creation of the world; The finitude, shape, and place of the world; The perfection of the world; The possibility of other worlds; Extracosmic void space. In each of these chapters Grant follows the debate in a chronological way, carefully presenting the various opinions, their points in common and their discrepancies. He devotes a particular attention in trying to assess, from the sometimes endless variations of opinions concerning a certain dispute, what were the truly popular conceptions and what were mere isolated speculations diverging from the general consensus and hardly relevant to the development of medieval cosmology.
The debates described in Part I show the changing and maturing of scholastic cosmology under the pressure of two different kinds of influences. In the thirteenth and fourteenth centuries the need to adapt the Aristotelian concepts with the Christian faith led to an intense debate within the scholastics. While Grant clearly does not fully endorse Duhem's thesis that "one can state that the excommunications delivered in Paris on March 7, 1277, by Bishop Etienne Tempier and the Doctors of Theology were the birth certificate of modern physics",3his book gives ample evidence to the extreme importance these condemnations had in breaking the conceptual straightjacket some Aristotelian propositions represented. Spurred by the need to preserve God's omnipotence and absolute freedom, medieval authors engaged in an intense critical evaluation of Peripatetic cosmology. The final outcome of such an effort was a decided rejection of some Aristotelian teachings (for example on the eternity of the universe or the radical impossibility of other worlds) or the adoption of an attitude where the possible veracity of the two sides in a dispute was preserved (for example when addressing the complex problem of the finitude of the world). A second challenge - and, in the end, a fatal one - faced medieval cosmology by mid-sixteenth century, when new observations of astronomical events and the appearance of Copernicus' De Revolutionibus, forced a radical reformulation of medieval cosmology.
Part II (Chapters 10 to 20) concerns the analysis of questions related to the celestial region itself: Its nature, properties, motions and relation to the terrestrial region. Following the medieval tradition, this is the part to which Grant devotes more space. It is impossible in a few paragraphs to convey the wealth of information contained in the approximately 500 pages that constitute part II. If the story of some of its chapters has already been told in other places - in a much more fragmented and disordered fashion, to be sure - other chapters are mines of new information. Although in this part of the book some of the debates and concepts of the thirteenth and fourteenth centuries are described, the most important aspects are those related to the need of sixteenth and seventeenth scholars to change the traditional view of the celestial realm under the pressing evidence of the new observations. Tycho Brahe's observation of a new star in 1572 and of a comet in the celestial region in 1577, and Galileo's telescopic observations starting in 1609 (satellites of Jupiter, sunspots, etc.), demanded a dramatic re-appraisal of the medieval ideas of celestial incorruptibility and hardness of the orbs. To this challenge renaissance scholastic authors responded with a surprising versatility and diversity of opinions which gives a sound credit to Grant's remark that "Scholastic Aristotelians of the late sixteenth and the seventeenth century were a diverse group about whom no easy generalizations are warranted." (p. 673)
Part II ends with a conclusion (Five centuries of cosmology), which, by analyzing the elements of tradition and innovation in scholastic cosmology, serves as a concise summary of the whole book. For those who, before starting to read the complete book, would like to have an idea, in a few pages, of its contents, I would recommend the reading of this conclusion as a first approach to the work.
After the two parts described, follow the appendices. Appendix I: Catalog of Questions on Medieval Cosmology, 1200-1687; and Appendix II: Anatomy of Cosmology. I would like to stress again the importance of the appendices. As already said, the whole book revolves around them, they are the backbone and the point of departure for the text. Appendix I is the list of questions selected, with authors and works from which they were drawn carefully identified. In Appendix II Grant presents a detailed analysis of the authors and works, as well as a general discussion on the methodology and criteria used for the choice of the material. A very complete bibliography and an excellent index culminate the book and make it a fundamental working reference for anyone with interests related to the ones analized.
As it is natural, in a book as ambitious as this one, critiques are bound to appear and most of them are certainly related to the choice of the materials presented. Grant is obviously aware of this and right in the first pages he declares: "(...) it seems wise to impose some order on the concept of medieval cosmology. A rationale for the inclusion and exclusion of topics and themes is desirable, as is the establishment of reasonable and appropriate bounds. These are formidable tasks, where decisions may sometimes seem arbitrary."(p. 5)
Some will complain that they are arbitrary indeed. Couldn't it be possible to write a book twice as large as this one, including the hordes of minor authors and texts in the subject? Was the rationale for the choice of questions a correct one? (By this I mean the following: are questions like, "Whether the prime mover is absolutely simple" (qu. 157), or "Whether a comet signifies the death of rulers"(qu. 350) really as important as: "Whether there are or could be more worlds" (qu. 62), or for instance: "Whether it is possible that a vacuum can exist naturally" (qu. 308), and therefore couldn't one have reduced the number of questions analyzed, and the extend of the book, without loosing any really relevant information, to, say, half?) Of course one could go on like this for ever. However, to all these hypothetical objections Prof. Grant answers with a well balanced and obviously hard-thought defense of the choices made, and, all in all, I think most students of medieval cosmology will agree with him. Furthermore, due to the nature of the book, in order to challenge Grant's choices a work of comparable magnitude had to be produced, and this, I think, is a task very few, if any, living medieval scholars are prepared to do.
A further remark concerns not the choice of individual questions, but the overall choice of the themes. The division of the book in its part I and part II, is, as Grant reveals (p. 618), to some extend inspired in Albert of Saxony questions on De Caelo. Despite being a reasonable choice, it leaves one with the impression that, even in a work such as this, devoted to cosmological themes, some more attention to the sublunar realm would have been desirable. In the same vein, I also regret the absence of questions and discussions on Time.
In summary, this is a work which will add a great amount of new information to the experts and which will reveal to the novices the contents of medieval cosmological conceptions, whose true nature is best summarized in the following quotation: "We should lay to rest the oft-repeated, but misleading, judgment that the medieval mind took comfort in a small, intimate universe, the coziness of which was shattered only in the seventeenth century with the gradual acceptance of its infinite extend. If any sense of coziness existed about the cosmos, it derived not from its size but from its assumed intelligibility." (p. 620)
Professor Grant's book is a beautiful piece of scholarship. It is a great work offered to the community of scholars and to the public in general, to which we should all be grateful for.