"We find in him," writes De Goeje, "that sober understanding which distinguished his fellow-tribesmen: dignity, tact, and equilibrium; qualities which are seldom found in people of morbid constitution: self-control in no small degree. Circumstances changed him from a Prophet to a Legislator and a Ruler, but for himself he sought nothing beyond the acknowledgment that he was Allah's Apostle, since this acknowledgment includes the whole of Islam. He was excitable, like every true Arab, and in the spiritual struggle which preceded his call this quality was stimulated to an extent that alarmed even himself; but that does not make him a visionary. He defends himself, by the most solemn asseveration, against the charge that what he had seen was an illusion of the senses. Why should not we believe him?"[343] CHAPTER V THE ORTHODOX CALIPHATE AND THE UMAYYAD DYNASTY The Caliphate--_i.e._, the period of the Caliphs or Successors of Muḥammad--extends over six centuries and a quarter (632-1258 A.D.), and falls into three clearly-marked divisions of very unequal length and diverse character. [Sidenote: The Orthodox Caliphate (632-661 A.D.).] The first division begins with the election of Abú Bakr, the first Caliph, in 632, and comes to an end with the assassination of ‘Alí, the Prophet's son-in-law and fourth successor, in 661. These four Caliphs are known as the Orthodox (_al-Ráshidún_), because they trod faithfully in the footsteps of the Prophet and ruled after his example in the holy city of Medína, with the assistance of his leading Companions, who constituted an informal Senate. [Sidenote: The Ummayyad Caliphate (661-750 A.D.).] The second division includes the Caliphs of the family of Umayya, from the accession of Mu‘áwiya in 661 to the great battle of the Záb in 750, when Marwán II, the last of his line, was defeated by the ‘Abbásids, who claimed the Caliphate as next of kin to the Prophet. According to Moslem notions the Umayyads were kings by right, Caliphs only by courtesy. They had, as we shall see, no spiritual title, and little enough religion of any sort. This dynasty, which had been raised and was upheld by the Syrian Arabs, transferred the seat of government from Medína to Damascus. [Sidenote: The ‘Abbásid Caliphate (750-1258 A.D.).] The third division is by far the longest and most important. Starting in 750 with the accession of Abu ’l-‘Abbás al-Saffáh, it presents an unbroken series of thirty-seven Caliphs of the same House, and culminates, after the lapse of half a millennium, in the sack of Baghdád, their magnificent capital, by the Mongol Húlágú (January, 1258). The ‘Abbásids were no less despotic than the Umayyads, but in a more enlightened fashion; for, while the latter had been purely Arab in feeling, the ‘Abbásids owed their throne to the Persian nationalists, and were imbued with Persian ideas, which introduced a new and fruitful element into Moslem civilisation.