"The Qur’an, then, seems to be the authentic root

of two disciplines whose mutual relations are controversial: formal systematic theology (kalam), and Sufism (tasawwuf). Sufism is typically absent from the madrasa curriculum, which gives pride of place to kalam. And kalam presents itself as a fiercely rationalistic discipline, according to some more so even than Islamic philosophy (falsafa). [19]  A standard kalam text such as Taftazani's (d.1390) Shar al-'Aqa’id devotes three quarters of its length to systematic metaphysics (ilahiyyat), with the remainder dedicated to issues of prophecy and the afterlife which can only be demonstrated through revelation. Such texts defined orthodoxy; yet they seem to have been less influential upon the minds of most Muslims than the passionate Sufism of the likes of Rumi, whose pessimism about kalam is evident.

 Here we are faced with an evolving tension within classical Islamic intellectual life and society of a kind which required – and occasionally delivered – brilliant reformers. It is striking that only in a few texts do we observe an attempt to provide a grand synthesis of the two approaches, which we might, to borrow European terminology, describe as the logical and the passional. Ghazali (d.1111) is the most obvious, and successful, example. Other claimants would include Ibn 'Arabi (d.1240), Ibn Kemal (d. 1534), Shah Wali Allah al-Dihlawi (d.1762), and Said Nursi (d. 1960), before we enter the purely modern period, where such synthetic theologies have been challenged by modernists and fundamentalists, both of whom, for different reasons, are uneasy with mysticism and kalam.

This synthetic renewal, which often draws in individuals acclaimed as the ‘renewers’ (mujaddid) of their centuries, [20]  is a key dynamic in Islamic religion and history. Hence tendencies perceived as erroneous, or even heretical, may be helpfully understood as the result of an imbalance towards one type of epistemology at the expense of the other. Sachiko Murata and William Chittick have reflected extensively on this inner Islamic metabolism, identifying kalam with the principle of drawing inferences about God as Transcendence (tanzih); and Sufism with the principle of experiencing God as Immanence (tashbih); the dyadic categorisation of divine names as Names of Rigour and Names of Beauty is one outcome. [21]  Their conclusion is that these two inexorable consequences of the postulate of monotheism run like twin constants through Islamic religious history. Each is allocated its own realm, form of discourse, and even, on occasion, ritual life and structured authority. 

-from pg. 6-7 of Shaykh Abdal-Hakim Murad's "Reason as Balance: the evolution of 'aql" (a paper for the Cambridge Muslim College)