  Revolutions in the celestial realm are the natural motions of the special element making up the celestial spheres. This, however, does not entail that they have no need of an external unmoved[45]  mover: the motions of the sublunary elements also occur under the influence of a moving cause. Nevertheless, the celestial bodies cannot be moved by an external mover of the same sort as the sublunary elements.  These celestial bodies are eternal and ungenerated. Consequently, Aristotle cannot appeal to the entity which produced them as responsible for their locomotions.  As they do not encounter any hindrance during their revolutions, there is no room for an accidental mover which would remove any obstacles in their way. Nevertheless, as celestial revolutions are motions, albeit eternal ones, they include some component of potentiality, which is actualised in the motion, and hence this potential component is in need of an actuality as a mover. This requirement implies that whatever can be the mover of these eternal motions needs to be in actuality without any restrictions (Metaphysics  12.6).[46]  Moreover, such an entity has to possess an infinite  power[47]  which it communicates to the moved celestial sphere. Hence, this entity cannot be divisible and cannot have extension (Physics 8.10).