Some of these thinkers use “substance” to mean that which occupies space; thus, for them, a body occupying space is a substance. They may also mean by it the indivisible atom: the part that cannot be divided. Thinkers disagree over its existence. The question is whether bodies are composed of indivisible atoms, of matter and form, or of neither. There are three views, the soundest being the third: bodies are composed neither of indivisible atoms nor of matter and form. This is the view of many groups among the speculative theologians, such as the Hishāmiyya, Dirāriyya, Najjāriyya, Kullābiyya, and many of the Karrāmiyya. It is also the view of the majority of jurists, hadith scholars, Sufis, and others. Indeed, it is the view of most rational thinkers, as has been explained at length elsewhere.
Those who apply the term “substance” to what occupies space disagree as to whether a substance that does not occupy space can exist. Some of them say that everything that exists is either a substance or an accident, and include the Necessary Existent within the designation “substance.” Others say that everything that exists is either a body or an accident, and include the Necessary Existent within the designation “body.” Both views have been held by some Muslim and non-Muslim speculative thinkers.
Among the philosophers and Christians are those who call Him a substance but not a body. It is also reported of one Muslim speculative thinker that he calls Him a body but not a substance, though, in his terminology, a body