Al-Ash`ari was born at Basra in 260 or 270, and died at Baghdad about 330 or 340. At first he was an adherent of the Mu`tazilites, but one Friday in A.H. 300 he made a public renunciation of the views of that party, and took up a definitely orthodox position; in the pulpit of the great mosque at Basra he said, “They who know me know who I am; as for those who do not know me, I am `Ali b. Isma`il al-Ash`ari, and I used to hold that the Qur´an was created, that the eyes of men shall not see God, and that we ourselves are the authors of our evil deeds; now I have returned to the truth; I renounce these opinions, and I take the engagement to refute the Mu`tazilites and expose their infamy and turpitude” (Ibn Khallikan, ii. 228). From this it will be perceived that the doctrines then regarded as characteristic of the Mu`tazilites were (i.) that the Qur´an was created, (ii.) the denial of the possibility of the beatific vision, and (iii.) the freedom of the will.

In the period after this change al-Ash`ari wrote a controversial work against the Mu`tazilites, which bears the name Kitab ash-Sharh wa-t-Tafsil, “the book of explanation and exposition”; he was the author also of religious treatises called Luma “flashes,” Mujaz “abridgment,” Idah al-Burhan “elucidation of the Burhan,” and Tabiyin “illustrations.” His real importance, however, lay in founding a school of orthodox scholasticism, afterwards more fully developed by al-Baqilani, and gradually spreading through the Muslim world, although strongly opposed on the one side by the falasifah, who saw in its teaching the introduction of traditional beliefs limiting and restricting the Aristotelian doctrine, and on the other side by the more reactionary orthodox, who disapproved the use of philosophical methods as applied to theological subjects. This use of philosophy in the explanation and defence of religion came to be known as kalam, and those who employed it were called mutakallamin.

In dealing with the old problems of Muslim theology, such as the eternity of the Qur´an, the freedom of the will, etc., the Ash`arites do seem to have produced a reasonable statement of doctrine, which yet safeguarded the main demands of orthodoxy.

(a) As to the Qur´an they held that it was eternal in God, but its expression in words and syllables was created in time. This does not of course mean that the expression was due to the Prophet to whom it was revealed, but to God, so that the doctrine of literal inspiration was asserted in the strictest form. Nor was it thus created when it was revealed, but long before in remote ages when it was first uttered to the angels and “august beings,” and was afterwards disclosed by the angel Gabriel to the Prophet Muhammad. This, which is now the orthodox belief, has furnished an opportunity for controversy to Christians and modern rationalists, who have fixed upon the use of particular words, introduced into Arabic as loan words from Syriac, Persian, and Greek, and appear in the Qur´an: how, they ask, can it be explained that words revealed at a remote period of past eternity, long before the creation of the world, as it is commonly asserted, show the influence of foreign languages which were brought to bear upon Arabic in the 7th cent. A.D.? and Muslim apologists, who have always maintained the absolute purity of Qur´anic Arabic as one of the evidences of Divine origin, seem to regard this as a serious difficulty. The view that the Qur´an is eternal in substance, and thus in substance revealed to the Prophet, who was left to express it in his own words, which would thereby show the limitations of his time, is not admitted by the orthodox. It will be noted also that the Ash`arite teaching evades and does not answer an old difficulty: if the substance of the Qur´an is the wisdom of God and is co-eternal with Him, even though emanating from Him, we have something other than God, namely, His wisdom, eternally existing with Him, and this can be represented as parallel with the persons of the Christian Trinity, so as to be inconsistent with the absolute unity of God.

(b) This brings us to the attributes of God generally. The Ash`arites in this controversy side with the traditional school against the philosophers. Of the ten Aristotelian categories they regard only two—existence, i.e., ens, and quality as objectively real; the other eight are merely relative characteristics (i´tibar) subjective in the mind of the knower, and having no objective reality. God has qualities—indeed, no less than twenty are enumerated, but amongst these is mukhalafa, which is the quality of uniqueness in qualification, so that the qualities and attributes ascribed to God must either be such as cannot be applied to men, or else, if the terms can be used of created beings, they must have quite different meanings when applied to God, and these qualities thus signified must be such as could not be predicated of men or of any other created being. Thus, that God has power and wisdom means that He is almighty and omniscient in a way which could not possibly be stated of any men. In practice this works so that no attribute can be applied to God unless it is expressly so applied in the text of the Qur´an; if it occurs there it may be used, but must be understood as having a meaning other than such a term would have when used in the normal way of men. It cannot be that God’s attributes differ from those of men only in degree, as that He is wiser and more powerful than man, but they differ in their whole nature. It is noted also that God is qiyam bi-n-nafs, or “subsisting in Himself,” that is to say, independent of any other than Himself, and so God’s knowledge does not depend on the existence or nature of the thing known.

(c) As to freedom of the will. God creates power in the man and creates also the choice, and He then creates the act corresponding to this power and choice. Thus the action is “acquired” by the creature.

Of the categories existence is the first substratum, and to this the other predicables are added: none of these others are separable or per se, they can only exist in the essence. It is admitted that such qualities exist in the ens, but they are only adjuncts which come into being with the ens and go out of existence with it. Therefore the world consists of entia or substances on which the mind reflects the qualities which are not in the thing itself but only in the mind. Against the Aristotelian theory that matter suffers the impress of form, he argues that all impress is subjective in the mind: if all qualities fall out substance itself ceases to exist, and so substance is not permanent but transitory, which opposes the Aristotelian doctrine of the eternity of matter.

The substances perceived by us are atoms which come into existence from vacuity and drop out of existence again. Thus, when a body moves from one position to another the atoms in the first position cease to be, and a group of new similar atoms come into existence in the second position, so that movement involves a series of annihilations and creations.

The cause of these changes is God, the only permanent and absolute reality. There is no secondary cause, as there are no laws of nature; in every case God acts directly upon each atom. Thus, fire does not cause burning, but God creates a being burned when fire touches a body, and the burning is directly His work. So in the freedom of the will, as, for example, when a man writes, God gives the will to write and causes the apparent motion of the pen and of the hand, and also directly creates the writing which seems to proceed from the pen.

Existence is the very self of the thing. This is peculiar to al-Ash`ari and his followers: all others hold existence to be the state (hāl) necessary to the essence, but in al-Ash`ari it is the essence. So God exists, and His existence is the self (`ayn) of His essence.