ADELARDO di BATH. — English by birth, he completed his studies at Tours and taught at Laon. Dissatisfied with the « gallica studia », he undertook long journeys through southern Italy, Sicily, where he enjoyed the favor of Guglielmo, bishop of Syracuse, the Near East, and Palestine. His direct familiarity with the scientific works of the Greeks and Arabs provided him with new and important materials for his favored studies of physics, astronomy, and mathematics. On returning to his homeland, he seems to have obtained some teaching position at the royal court; meanwhile, he devoted himself to compiling treatises in dialogical form and preparing versions to make the philosophy and sciences of Mediterranean culture accessible to the West. His death is placed around 1160.
Works certainly authentic are: De eodem et diversio, ed. H. Willner (Bacumher Beitr., IV, 1, Münster in V. 1903); Perdifficiles quaestiones naturales, translated into Hebrew toward the end of the 13th century, as M. Steinschneider demonstrated (Die hebr. Uebersetzungen..., Berlin 1893, § 275, p. 464), and published toward the end of the 1500s; Regulae abaci, published by Boncompagni in his Bullettino della biografia e della storia delle scienze, 14 (1881), pp. 1–134; Eish Elkauresni, a version of the astronomical tables of al-Khuwarizmi (1126); Elementi di Euclide, translated from Arabic; L'Astrolabio and De cura accipitrum, which is a treatise on falcon hunting (ed. A. E. H. Swain, Göttingen 1937).
In the controversy concerning universals, A. opposed exaggerated realism, and his solution makes him a precursor of Abelard. In the Quaestiones naturales, his spirit of observation frequently stands out, while there he denounces the laziness of those who merely repeat and calls authority the halter (capistrum) of the intellect. In physiology he leaves Aristotle to follow Galen and the Salernitan physicians; he enunciates the principle of the continuity of nature and the indestructibility of matter, and seems to have been the first among the Latins to use the way of motion to prove the existence of God. A. occupies a foremost position in the development of science, not only in the 12th century but throughout the entire Middle Ages; he is the pioneer of the scientific method, which he succeeded in combining with an exquisite taste for classical antiquity, revealed by his passionate investigations into Greek and Arabic works and recognizable in the unmistakable style of his writings, which recalls the classical models.