Unmoved mover
| Latin | Primum movens immobile; motor immobilis |
|---|---|
| Treatise | Summa theologiae I, q. 2 a. 3 |
| Controlling authority | Dei Filius; Catechism 31–35 and 199–221 |
| Doctrinal standing | God exists and can be known from creatures; the first way is a philosophical demonstration |
| School | Thomism |
Unmoved mover is, in the first of Aquinas's five ways, the first cause of motion that is not itself reduced from potency to act, which everyone understands to be God.[1]
The argument from motion
Summa theologiae I, question 2, article 3, opens the five ways with the argument from motion as the first and more manifest. It is certain and evident to the senses that some things are in motion. Whatever is in motion is put in motion by another, because motion is the reduction of something from potentiality to actuality, and nothing reduces itself in the same respect. An infinite series of moved movers would yield no first mover, and therefore no motion. It is necessary to arrive at a first mover put in motion by no other.[1]
The 1913 Catholic Encyclopedia article on the existence of God surveys demonstrations of that truth, including the argument from motion used in the first way. The argument is a posteriori, from effects better known to us. Question 2, article 1, had already denied that God's existence is self-evident to us, though it is self-evident in itself because in God essence and existence are identical. Article 2 had shown that demonstration from effects is possible even when the effects are not proportionate to the cause.[2][3]
Motion, potency, and ordered movers
Motion here is broader than local displacement. It is any reduction from potency to act: alteration, growth, generation, even the passage from not seeing to seeing. The staff moves because the hand moves. The series in view is of essentially ordered causes here and now, not a search for the earliest event in cosmic history. To confuse the two is to miss the argument and then to declare it obsolete because physics has a different story of beginnings.
The first mover is unmoved because it is act without the potency that would require a further mover. Later questions identify this with pure act, with ipsum esse subsistens, and with the God of Abraham only after the ways have reached a first cause to which all give the name God. The identification is philosophical theology. It is not a claim that Aristotle's Physics is a book of Joshua.
Demonstration and the God of faith
Dei Filius teaches that God, the beginning and end of all things, can be known with certainty from created things by the natural light of human reason. The Catechism repeats that teaching and then adds that there are also many obstacles to such knowledge, so that revelation is morally necessary. The first way is one classical form of the demonstration the council affirms. It is not the council's own wording, and it is not the only possible faithful demonstration.[4][5]
The God reached as unmoved mover is the same God confessed in the creed, not a rival deity of the philosophers. The five ways do not replace the living God of Scripture. They show that the world, as moved, caused, contingent, graded, and governed, is unintelligible without him. Faith presupposes natural knowledge as grace presupposes nature, even when a given believer accepts God's existence on authority because he cannot follow a proof.
What the first way does not claim
The argument does not claim that every physical theory of motion is false, or that God is the next push after the last particle. It does not claim that an infinite temporal series of accidental causes is impossible. It claims that a series of moved movers, as moved, requires an unmoved source of act. Aeterni Patris and Fides et Ratio commend this style of demonstration as part of Christian philosophy's service to the faith, without making the five ways a sixth article of the creed.[6]
Objections from evil and from the sufficiency of nature are answered in the same article: God permits evil to bring good from it, and nature itself must be traced to a first cause. Those replies belong to theodicy and to the doctrine of creation. The unmoved mover is the first step of that path, not the whole of Catholic natural theology, and not a school mascot to be used against other faithful proofs.
References
- Back to citation occurrence 1.0 Back to citation occurrence 1.1 Thomas Aquinas, Summa theologiae I, question 2, article 3 — Primary five ways, including the argument from motion to an unmoved mover and the argument from ordered efficient causes.
- Back to citation Catholic Encyclopedia (1913), Existence of God — Public-domain survey of demonstrations that God exists, including the argument from motion used in the first way.
- Back to citation Catechism of the Catholic Church, 199–221 — Authoritative confession of the one God, his simplicity, fullness of being, and the identity of his essence with his existence.
- Back to citation First Vatican Council, Dei Filius — Dogmatic constitution on God the Creator, the natural knowability of God, the distinction of the natural and supernatural orders, and the gratuity of revelation.
- Back to citation Catechism of the Catholic Church, 31–35 — Authoritative teaching that God can be known with certainty from created things by the natural light of human reason.
- Back to citation Leo XIII, Aeterni Patris — Encyclical restoring Christian philosophy in the school of Thomas Aquinas while distinguishing that commendation from a definition of every Thomistic thesis.