for a particular sound to be eternal; for whatever is necessarily eternal must persist and cannot cease to exist.

By written letters, one may mean the actual shape formed in ink, or a corresponding form of the same dimensions, such as a shape fashioned in stone or paper. Removing some of its parts demonstrates that it had a beginning. Alternatively, “letters” may mean the ink itself.

As for spoken letters, these may likewise mean the segmented sounds combined together, or they may mean the boundaries and extremities of sounds, just as the word harf, when applied to a physical body, means its edge or extremity. Thus, one speaks of the edge of a loaf, the edge of a mountain, and the like. This is also its meaning in the words of Allah Most High:

“Among people are those who worship Allah on an edge.”

“Letters” may also mean the inwardly imagined letters: the composed, ordered speech that takes shape within a person before he utters it. People have differed over whether letters can exist without sounds in a living being capable of speech, holding two views on the matter. Accordingly, this group, which maintains that individual letters are eternal, differed over whether they can be eternal without eternal sounds, or whether there must necessarily be eternal sounds that have always existed and will always exist.

Those who maintain that particular sounds are eternal then differed over what is heard from the reciter: is the eternal sound heard from him? Some said: “What is heard is the eternal sound.” Others said: “Rather, what is heard consists of two sounds, one eternal and the other originated. Whatever is indispensable to the Quran’s existence is eternal, while whatever is additional to that is originated.”