[“God did not create anything except for a purpose”]:
Muslims know with certainty that God has created nothing without a wise purpose; that very purpose is what renders each created thing good and beautiful. Hence, within creation there is no sheer, unmixed evil that contains no benefit whatsoever. This is the meaning of the Prophet’s words, “Evil is not attributed to You,” and the reason why the Qur’an never ascribes evil to God alone. Rather, it is mentioned in general terms, or linked to its underlying cause, or expressed in a passive construction with the agent omitted.

So the particular, restricted evil that does exist has a cause, and that cause is either an absence or a presence. The “absence” refers to the lack of a necessary condition or part of an effective cause; for pure non-existence can never be a complete cause for the coming-to-be of anything. In such cases the elements that would have produced good and delight are in place, but the required condition is missing, and thus pain ensues. Examples include the failure to perform obligatory duties—which results in blame and punishment—the absence of knowledge, which brings about the pain of ignorance, the lack of hearing, sight, and speech, which produces the suffering of blindness, deafness, and muteness, and the loss of health and strength, which leads to the pain of illness and weakness.