If the other Christian sects failed to exhibit the same vigorous life, it was not the fault of the Muhammadans. All were tolerated alike by the supreme government, and furthermore were prevented from persecuting one another. [146] In the fifth century, Barsauma, a Nestorian bishop, had persuaded the Persian king to set on foot a fierce persecution of the Orthodox Church, by representing Nestorius as a friend of the Persians and his doctrines as approximating to their own; as many as 7800 of the Orthodox clergy, with an enormous number of laymen, are said to have been butchered during this persecution. [147] Another persecution was instituted against the Orthodox by Khusrau II, after the invasion of Persia by Heraclius, at the instigation of a Jacobite, who persuaded the King that the Orthodox would always be favourably inclined towards the Byzantines. [148] But the principles of Muslim toleration forbade such acts of injustice as these: on the contrary, it seems to have been their endeavour to deal fairly by all their Christian subjects: e.g. after the conquest of Egypt, the Jacobites took advantage of the expulsion of the Byzantine authorities to rob the Orthodox of their churches, but later they were restored by the Muhammadans to their rightful owners when these had made good their claim to possess them. [149] In view of the toleration thus extended to their Christian subjects in the early period of the Muslim rule, the common hypothesis of the sword as the factor of conversion seems hardly satisfactory, and we are compelled to seek for other motives than that of persecution. But unfortunately very few details are forthcoming and we are obliged to have recourse to conjecture. [150] In an age so prolific of theological speculation, there may well have been some thinkers whose trend of thought had prepared them for the acceptance of the Muhammadan position. Such were those Shahrīghān or landed proprietors in Persia in the eighth century, who were nominally Christians, but maintained that Christ was an ordinary man and that he was as one of the Prophets. [151] They appear at times to have given a good deal of trouble to the Nestorian clergy, who were at great pains to draw them into the paths of orthodoxy; [152] but their theological position was more closely akin to Islam than to Christian doctrine, and they probably went to swell the ranks of the converts after the Arab conquest of the Persian empire.