Primum Mobilè

the primitive moveable element, is, in its proper signification, the original matter of the world (primae materia). The ancients understood by it the exterior hollow sphere, which was supposed to include and put in motion the remainder of the universe (fixed stars and planets): a quite arbitrary supposition. Primal mover would l)e the principle of all motion, or the first moving cause. According to Aristotle, this cause is God, who, while motionless himself, puts all the rest in motion, and is therefore called by the philosopher τὸ πρῶτον κινοῦν. See Aristotle, Phys. 8:5; De generat. et corrupt. 1, 7: 2, 7.