There are different classes of men who fall roughly into three groups. The highest of these are those whose religious belief is based on demonstration (_burhan_), the result of reasoning from syllogisms which are _à priori_ certain; these are the men to whom the philosopher makes his appeal. The lowest stratum contains those whose faith is based on the authority of a teacher or on presumptions which cannot be argued out and are not due to the exercise of pure reason; it is mischievous to put “demonstration” or reason or controversy before people of this type, for it can only cause them doubt and difficulty. Intermediate between these two strata are those who have not attained the use of pure reason--which, with Ibn Rushd, seems to be simply intuition--but are capable of argument and controversy by means of which their faith can be defended and proved; “demonstration” proper is not to be laid before these, but it is right to enter into argument with them and to assist them to rise above the level of those whose belief is based only upon authority. Most of all, Ibn Rushd opposed the teaching of the _mutakallimin_ or orthodox scholastic theologians, whom he regarded as subverting the pure principles of the Aristotelian philosophy, and of these he considered the worst to be al-Ghazali, “that renegade of philosophy.” His leading controversial work is the _Destruction of the Destruction_ (Tahafat at-Tahafat), which he designed as a refutation of al-Ghazali’s _Destruction of the Philosophers_. But it was as a commentator on the text of Aristotle that he became best known to subsequent generations amongst the Jews and the later Latin scholastics; he was the great and final commentator. Strangely, however, Ibn Rushd never perceived the importance of reading Aristotle in the original; he had no knowledge of Greek, and gives no sign of supposing that a study of the Greek text would at all assist a student of the philosopher. The method of his commentaries is the time-honoured form derived from the Syriac commentators: a sentence of the text is given and the explanatory comments follow.