[75] Of course, extrahistorical and, so to speak, personalistic explanations are possible. In his time, V. O. Kliuchevskii considered the Oprichnina, though monstrous, to be an episode in Russian history which was in a certain sense accidental, and in considerable degree conditioned by the personality of Ivan the Terrible. In developing this line of reasoning, the leading modern historians of the Muscovite period in the United States, Richard Hellie and Edward Keenan, offer medical explanations for the Oprichnina. According to Hellie, Ivan the Terrible's actions are to be explained by paranoia; according to Keenan, by physical disease, arthritis and spondylitis, which made him incapable of fulfilling his duties as tsar. (See Edward Keenan, "Vita: Ivan Vasil'evich, Terrible Tsar 1530-1584," p. 49; Richard Hellie, "In Search of Ivan the Terrible," Preface to S. F. Platonov's
[76] Ibid., p. 46.
[78] Ibid., p. 247.
[79] Ibid., p. 249. Emphasis added.