intro
5. The main part of the dialogue is of extraordinary interest for the history of astronomy, cosmology, geography, and catoptrics; and this aspect of the work deserves more attention than it has usually received.J. O. Thomson, History of Ancient Geography (Cambridge, 1948), pp. 330 f., gives a brief outline of this part of the work and cites Duhem’s and Humboldt’s praise of it. A. O. Prickard has some general remarks on the subject in the introductions to his two translations of the dialogue (Plutarch on the Face which appears on the Orb of the Moon [Winchester and London, 1911], pp. 9-15, and Plutarch: Select Essays, ii [Oxford, 1918], pp. 246-253). So has S. Günther in his outline of the dialogue, Vergleichende Mondund Erdkunde (Braunschweig, 1911), pp. 24-35, nearly half of which, however, is concerned with the myth. Hirzel in his treatment of the dialogue (r Dialog [Leipzig, 1895], ii, pp. 182-189) has little or nothing specific to say of its scientific aspect. The most extensive monograph on the dialogue, Maximilian Adler’s Quibus Ex Fontibus Plutarchus Libellum De Facie in Orbe Lunae Hauserit (Diss. Phil. Vind. x [1910], pp. 85-180), is concerned with the scientific passages only in so far as the author thinks that from them he can draw support for his thesis that Posidonius was Plutarch’s source for the dialogue. A similar purpose limits the treatment of the work by K. Praechter in his Hierokles der Stoiker (Leipzig, 1901), p. 26 and pp. 109-120. cf. also the notes of W. Norlind, Eranos, xxv (1927), pp. 265-277. It is not a technical scientific treatise and is not to be judged as if it were meant to be such; but it is all the more significant that in a literary work intended for an educated but non-technical audience towards the end of the first century a.d. Hipparchus and Aristarchus of Samos are familiarly cited and a technical work of the latter is quoted verbatim, the laws of reflection are debated, the doctrine of natural motion to the universal centre is rejected, and stress is laid upon the cosmological importance of the velocity of heavenly bodies. It is interesting to compare the treatise of Ibn Al-Haitham (965-1039) which was translated from the Arabic by Carl Schoy under the title Abhandlung des Schaichs Ibn Alî Al-Hasan Ibn Al-Hasan Ibn Al-Haitham: über die Natur der Spuren [Flecken], die man auf der Oberfläche des Mondes sieht (Hannover, 1925). Ibn Al-Haitham’s explanation of the face is that the nature of the moon’s substance must differ from place to place, since the variation in illumination can be the result only of a difference in the power to absorb and reflect light, and the spots are places of greater density and less power of absorption (pp. 20 ff. and 29-31). Though Schoy appears to have been unaware of it and Plutarch does not mention it, this explanation is ascribed to οἱ ἀρὸ τῶν μαθηματικῶν in Aëtius, ii. 30. 7 (Dox. Graeci, p. 362. 5-13). Ibn Al-Haitham rejects the theory that the spots are shadows cast by prominences on the moon, arguing that such shadows would not always have the same shape and position, as the spots do (pp. 14-17). Like Plutarch, however, he knows and refutes the notion that they are a reflection of the terrestrial ocean or any other terrestrial feature (pp. 1-2, 5-7; Facie, chaps. 3-4); and he also adduces the colour of the moon in eclipse (pp. 31 f.; Facie, 934 B - D). He proves impossible as well (pp. 4-5, cf. p. 2) an explanation unmentioned by Plutarch but recorded by Simplicius ( Caelo, p. 457. 25-30) that the spots are the result of vapours rising from below and obscuring the moon’s brilliance (cf., however, for something similar, Milton, Paradise Lost, v. 415-420, and Facie, 922 B - C). Like Cleomedes (ii. 4. 103 [p. 186. 14-27 Ziegler]), Ibn Al-Haitham seems to hold that the moon as a reflecting convex mirror would have to appear as a single point of light (pp. 7 f. with Schoy’s note, p. 8, n. 1). Most of the attention given to the dialogue, however, has been attracted by the concluding myth.It was probably the myth as much as the more strictly astronomical part of the dialogue that caused Kepler to make his Latin translation and commentary of the Facie, which he did shortly before his death. This is printed in volume viii of Joannis Kepleri Opera Omnia, ed. Dr. Ch. Frisch (Francofurti a. M., 1870). cf. R. Schmertosch, Keppler zu Plutarchs Schrift Vom Gesicht im Monde, Phil.-Hist. Beiträge Curt Wachsmuth zum 60. Geburtstag überreicht (Leipzig, 1897), pp. 52-55, and R. Pixis, Kepler als Geograph (Munich, 1899). This consists of two parts. The second and main part is the eschatological myth, which establishes the purpose of the moon in the cosmos by explaining her role in the life-cycle of souls and which the stranger told Sulla he had from the chamberlains of Cronus (942 D 945 D); the first is the introduction to this myth or frame-story, in which the stranger explained to Sulla how from the continent on the other side of the Atlantic he came to the Isle of Cronus, one of several that lie westwards of Britain, and thence, after having served thirty years, travelled to Carthage where he met Sulla (941 A 942 C).
