(Ἀρεταῖος), one of the most celebrated of the ancient Greek physicians, of whose life, however, no particulars are known. There is some uncertainty respecting both his age and country ; but it seems probable that he practised in the first century after Christ, in the reign of Nero or Vespasian, and he is generally styled " the Cappadocian" (Καππάδοξ). He wrote in Ionic Greek a general treatise on diseases, which is still extant, and is certainly one of the most valuable reliques of antiquity, displaying great accuracy in the detail of symptoms, and in seizing the diagnostic character of diseases. In his practice he followed for the most part the method of Hippocrates, but he paid less attention to what have been styled " the natural actions" of the system; and, contrary to the practice of the Father of Medicine, he did not hesitate to attempt to counteract them, when they appeared to him to be injurious. The account which he gives of his treatment of various diseases indicates a simple and sagacious system, and one of more energy than that of the professed Methodici. Thus he freely administered active purgatives; he did not object to narcotics; he was much less averse to bleeding; and upon the whole his Materia Medica was both ample and efficient. It may be asserted generally that there are few of the ancient physicians, since the time of Hippocrates, who appear to have been less biassed by attachment to any peculiar set of opinions, and whose account of the phenomena and treatment of disease has better stood the test of subsequent experience. Aretaeus is placed by some writers among the Pneumatici (Dict. of Ant. s. v. Pneumatici), because he maintained the doctrines which are peculiar to this sect; other systematic writers, however, think that he is better entitled to be placed with the Eclectics. (Dict. of Ant. s. v. Eclectici.)