By a brother:
The science of tazkiyah (spiritual purification) has been known by derivatives of the word taṣawwuf from as early as the second century, just as the science of Islamic law has been known as fiqh for many centuries. There can be no considerable difference of opinion on the permissibility of using the term taṣawwuf to refer to the ❝science of spiritual purification❞ as people are permitted to coin any term they prefer for any meaning.
The usual response to the above by some is, ❝Did the Prophet ﷺ or the companions use the word taṣawwuf to refer to tazkiyah?❞ The answer again is: It doesn’t really matter. There is no prohibition in using a term that the Messenger ﷺ or his companions did not use. In fact, we do this in many sciences including ‘aqīdah (theology) itself; for the word ‘aqīdah was not used by the Messenger ﷺ or his companions to refer to theology. However, that is not reason enough to discredit it.
In fact, even the word ❝fiqh❞ itself, as used by jurists for centuries, is not entirely the same as the meaning of ❝fiqh❞ in the Quran or the Sunnah. Sacred texts usually use the word fiqh to mean ❝the understanding of religion❞ in general, whereas scholars have been using the word ❝fiqh❞ to mean ❝Islamic law❞ for the better part of Islamic history.
The second response usually is that: ❝Unlike other nomenclature and terms, taṣawwuf had been tainted by foul practices.❞ Whilst it is true that some forms of taṣawwuf (the science of spiritual purification) had been tainted by foul practices, this is also true for all other sciences including ‘aqīdah itself. For instance, some strongly believe in the idea of ‘infinite regression of causes’ which is considered disbelief by the consensus of the Islamic scholars throughout the centuries and is one of the arguments used by some atheists today to explain away the existence of God. However, some insist that this should be considered true ‘aqīdah.
Would it be appropriate to discontinue using the term ‘aqīdah because of the aforesaid consequential mistake or other such mistakes that some or many may have made? The obvious answer is no. By the same logic, because of some mistakes of specific individuals in the field of taṣawwuf (spiritual purification), the term itself cannot and should not be rejected.
N.B. Suggesting that other linguistic derivatives of the technical term ‘aqīdah are found in a few traditions doesn’t change the reality that the word ‘aqīdah itself as coined later is not found in sacred texts. In this way, taṣawwuf, and ‘aqīdah are the same.