To the student of the history of science, Hildegard’s beliefs as to the nature and structure of the universe are among the most interesting that she has to impart. Her earlier theories are in some respects unique among mediaeval writers, and we possess in the Wiesbaden Codex B a diagram enabling us to interpret her views with a definiteness and certainty that would otherwise be impossible.
Hildegard’s universe is geocentric, and consists of a spherical earth,[52] around which are arranged a number of concentric shells or zones. The inner zones are spherical, the outer oval, and the outermost of all egg-shaped, with one end prolonged and more pointed than the other Fig. ([2]). The concentric structure is a commonplace of mediaeval science, and is encountered, for instance, in the works of Bede, Isidore, Alexander of Neckam, Roger Bacon, Albertus Magnus, and Dante. To all these writers, however, the universe is spherical. The egg-shape is peculiar to Hildegard. Many of the Mappaemundi of the Beatus and other types exhibit the surface of the habitable earth itself as oval, and it was from such charts that Hildegard probably gained her conception of an oval universe. In her method of orientation also she follows these maps, placing the east at the top of the page where we are accustomed to place the north.[53]
It is unfortunate that she does not deal with geography in the restricted sense, and so we are not in full possession of her views on the antipodes, a subject of frequent derision to patristic and of misconception to scholastic writers. She does, however, vaguely refer to the inversion of seasons and climates in the opposite hemisphere,[54] though she confuses the issue by the adoption of a theory widespread in the Middle Ages and reproduced in the Divina Commedia, that the antipodean surface of the earth is uninhabitable, since it is either beneath the ocean or in the mouth of the Dragon[55] (Plate [XI], cp. Fig. [4]). The nature of the antipodean inversion of climates was clearly grasped by her contemporary, Herrade de Landsberg (Fig. [5]).
Hildegard’s views as to the internal structure of the terrestrial sphere are also somewhat difficult to follow. Her obscure and confused doctrine of Purgatory and Hell has puzzled other writers besides ourselves,[56] nor need we consider it here, but she held that the interior of the earth contained two vast spaces shaped like truncated cones, where punishment was meted out and whence many evil things had issue.[57] Her whole scheme presents analogies as well as contrasts to that of her kindred spirit Dante.[58] Hildegard, however, who died before the thirteenth century had dawned, presents us with a scheme far less definite and elaborated than that of her great successor, who had all the stores of the golden age of scholasticism on which to draw.
In Hildegard’s first diagram of the universe, which is of the nature of an ‘optical section’, the world, the sphaera elementorum of Johannes Sacro Bosco and other mediaeval writers, is diagrammatically represented as compounded of earth, air, fire, and water confusedly mixed in what her younger contemporary, Alexander of Neckam (1157–1217), calls ‘a certain concordant discord of the elements’. In the illustrations to the Wiesbaden Codex B the four elements have each a conventional method of representation, which appears again and again in the different miniatures (Fig. [2] and Plates [XII] and [XIII]).
Around this world with its four elements is spread the atmosphere, the aer lucidus or alba pellis, diagrammatically represented, like the earth which it enwraps, as circular. Through this alba pellis no creature of earth can penetrate. Beyond are ranged in order four further shells or zones. Each zone contains one of the cardinal winds, and each cardinal wind is accompanied by two accessory winds, represented in the traditional fashion by the breath of supernatural beings.
Of the four outer zones the first is the aer aquosus, also round, from which blows the east wind. In the outer part of the aer aquosus float the clouds, and according as they contract or expand or are blown aside, the heavenly bodies above are revealed or concealed.
Enwrapping the aer aquosus is the purus aether, the widest of all the zones. The long axis of this, as of the remaining outer shells, is in the direction from east to west, thus determining the path of movement of the heavenly bodies. Scattered through the purus aether are the constellations of the fixed stars, and arranged along the long axis are the moon and the two inner planets. From this zone blows the west wind. The position and constitution of this purus aether is evidently the result of some misinterpretation of Aristotelian writings.
The next zone, the umbrosa pellis or ignis niger, is a narrow dark shell, whence proceed the more dramatic meteorological events. Here, following on the hints of the Wisdom of Solomon (chap. v) and the Book of Job (chap. xxxviii), are situated the diagrammatically portrayed treasuries of lightning and of hail. From here the tempestuous north wind bursts forth. This ignis niger is clearly comparable to the dry earthy exhalation that works of the Peripatetic school regard as given off by the outer fiery zone. The presence of the ignis niger thus suggests some contact on the part of the authoress with the teaching of the Meteorologica of Aristotle.[59]
The outermost layer of all is a mass of flames, the lucidus ignis. Here are the sun and the three outer planets, and from here the south wind pours its scorching breath (Fig. [2]).