In order to make proselytes, ʿAbdullah’s missionaries used to propose obscure questions about the Qurʾan and the doctrines of traditional Islam, with the object of showing that as generally held these doctrines were contrary to reason, and so required an explanation. The revelation of Islam, they said, was difficult, and hence there was much diversity of opinion and many sects and schools of thought, all of which caused an infinite amount of disedification and much trouble. The reason of these diverse opinions is that each man follows his own private judgment and forms his own conjectures, with the result that many end in utter unbelief. But God would not give a revelation full of such obscurity and ambiguity as the only guidance for men. It must be that there is some available guidance, some authoritative teacher who can explain the doctrine so that it may be both clear and certain, and such an infallible teacher implies an Imam. The _daʿi_ then gave illustrations of the obscurities and difficulties which men are not able to understand by the light of their own reason. The pilgrims at Mecca throw stones and run between the two hills, Safa and Merwa,—what is the purpose and meaning of this? Why is it that a woman who has omitted a fast and prayer because prevented by reasons of personal impurity is required to fast afterwards to make up for her omission, but is not required to make up for the omitted prayer? Why did God take six days to create the world when he could quite well have created it in an hour? What does the Qurʾan mean when he refers in a figurative manner to the “way”? What is the meaning of the reference to the two angels who write and take note?—why cannot we see them? What really are the torments of hell? What mean the words “and over them on that day eight shall bear up the throne of thy Lord”? (Qur., 69, 17). What is Iblis?—Who are Yajuj and Majuj (Qur., 18, 93), and Harut and Marut (Qur., 2, 96)? Why have there been created seven heavens, and seven earths, and why are there seven verses in the Fatha? and many similar questions all designed to show that the Qurʾan is full of references to things which are not explained and need explaining, but to which the orthodox teachers are unable to give an explanation. All these are the conventional arguments which are commonly employed to prove that revelation is incomplete without an authorised teacher.