Islam differs from Christianity by not having a strict hierarchical order. There is no official ‘magisterium’ by which the Muslim is judged orthodox. To a large degree the attestation of tawhid is the baseline for orthodoxy, and from this testimony, simple in itself, the individual may proceed to realize Divine Unity more or less depending on his abilities and inclinations, but without strict reference to an external authority or a sacramental economy. While there have been (and still are) exceptional situations where a group took it upon themselves to judge the faith of other Muslims, this has not been the norm, and there has never been anything in the Islamic world that even loosely resembled the Inquisition in the West.
It may be that this egalitarianism is what has permitted certain interpretations to flourish that were often combatted in Christianity, to its own detriment. We are thinking here of the way Sufism has been accepted and perceived in Islam, as opposed to the way the mystics of Christianity have been dealt with in Christianity. It has been said that in the Islamic world there is not a ditch digger who is not familiar with some poem of Rumi; on the other hand, in Christianity, no one but stuffy academics and fringe groups are familiar with Meister Eckhart.
This seems paradoxical, for what it means is that the egalitarian, levelling framework of Islam seems to have resulted in a more effective popularization of the work of the loftiest contemplatives of that tradition, while in Christendom, with its carefully constructed dogmatic systems, the average believer dwells at the baseline and is rarely exposed to the more colorful heights of their own spiritual heritage.
We do not, of course, make these comparisons in order to illustrate the inferiority or superiority of one tradition over another: we could easily highlight the advantages of the Roman hierarchical approach. Rather, we frame Islam here for its strengths and its victories, acknowledging that these are its own gifts and never offering them as recommendations for another tradition to emulate. Christianity is precisely what it ought to be, and what is important for us to convey here is that Islam too has its reason for being and brings with it, for the world for which it was made, certain advantages that no other revelation could have provided.