a necessary condition for that volition to be able to effectuate the subsequent step, and the sequence proceeds in this manner until the end of the path.

From this they infer that there must be an eternal, unceasing motion standing between the First Principle and the transient occurrences we witness. This perpetual motion cannot be rectilinear, for that would require the existence of infinite linear dimensions—an impossibility. Therefore the intermediary body must move in a circle, and that body is the celestial sphere.

It follows that the motions of the heavenly spheres are the proximate causes of the events that arise in this world. Because the sphere is a simple body, all its parts are alike, and the relations among the qualities of homogeneous parts are themselves homogeneous. But things that are entirely alike in their very essence cannot be causes of heterogeneous effects. Hence the celestial spheres must contain bodies of differing natures whose relative positions and configurations vary; only thus can those configurations serve as principles for the diverse happenings in our world. The bodies of distinct natures embedded in the spheres are the planets, and so the immediate causes of generation and corruption in the sublunary realm are the planetary conjunctions.

Al-Rāzī says: “The adherents of this view—the philosophers and the Sabians—went so far as to attribute lordship to these planets, devoted themselves to worshipping them, erected for each one a specific temple and a particular idol, and busied themselves in their service,” and he continues at length.

I reply: This is the furthest refinement of their foundational doctrine and the conclusion they seek to establish. Yet, to anyone who understands the real nature of the premises of this argument, it actually points to the very opposite of what they intend; for affirming a complete and sufficient cause existing from eternity