 Underlying all change, and enduring through it, is homogeneous matter, defined simply by its potentiality—that is, its potential to serve as subject for any earthly form (SubstOrb 1.50). Conceived of without form, it is perpetually enduring and numerically one everywhere: “all transient bodies share this body that is numerically one” (SubstOrb 2.87), because it is “deprived of the divisions of individual forms” (LongMeta XII.14 {1473}). Ibn Rushd worries in predictable ways about the reality of this so-called prime matter (mādda ʾūlā). On the one hand, he consistently counts it as a substance (e.g., ParaAnima 2.115). On the other hand, matter so-conceived is a “pure privation” and “does not exist outside of the soul” (LongMeta XII.14 {1473–4}). He offers the less-than-perspicuous compromise formula that prime matter lies “halfway, as it were, between absolute non-being and actual being” (quasi medium inter non-esse simpliciter et esse in actu) (LongPhys I.70; ParaPhys I.3.3.276).