In the second half of the nineteenth century European scholars were attracted by some of the views of the Mu'tazilites and studied them with great sympathy. In an account of them published in 1865 Heinrich Steiner of Zürich spoke of them as 'the free-thinkers of Islam'. At this period the later Sunnite philosophical theology or Kalām was little known in Europe and still less appreciated. The Mu'tazilites were seen as standing for freedom of the will and human responsibility; in other respects they adopted sensible, almost nineteenth-century liberal attitudes. It was felt that Islam would have been ever so much more congenial to the European if only the Mu'tazilites had not been replaced by the dry-as-dust, hide-bound, hair-splitting Ash'arites and their like. In the twentieth century, however, Western scholars gradually realized that this whole conception of the Mu'tazilites was inaccurate. They were not free-thinkers but quite definite Muslims, even if they indulged in speculation on some points; and, far from being liberal in outlook, they were behind the unhappy episode of the 'Inquisition' in the ninth century. In other ways, too, their theological views were linked with the politics of the day. Finally it was realized that some at least had been zealous apologists for Islam towards members of other religions.

The Mu'tazilites who attracted the European scholars and who were important in the history of Islamic theology were those who were involved in the process of bringing Greek conceptions into the discussions of Islamic dogma, that is, in the first elaboration of the discipline of Kalām. As has just been indicated, the name 'Mu'tazilite' was at first used in a fairly wide sense to include men like Ḍirār ibn-'Amr, but was later restricted to those who accepted the five points of the Mu'tazilite dogmatic position (to be enumerated later). Nowadays 'Mu'tazilite' is normally used only in the restricted sense by both Muslim and Western scholars, and this usage is followed here.