The First Way: Argument from Motion

Thomas Aquinas

The argument is valid.

Every inference was checked by machine.

Open in the playground

flowchart TD
    classDef axiom fill:#f6efd9,stroke:#a8842a,color:#23212b;
    classDef premise fill:#e7edf7,stroke:#1f4e9c,color:#23212b;
    classDef deduction fill:#f3f4f1,stroke:#5b6b85,color:#23212b;
    classDef conclusion fill:#d6e1f3,stroke:#1f4e9c,stroke-width:3px,color:#23212b;
    classDef objection fill:#f7e3e1,stroke:#b3261e,color:#23212b;
    classDef reply fill:#f3f4f1,stroke:#7a5c2e,color:#23212b;
    classDef imported stroke-dasharray:4 3;
    classDef defeated fill:#f3f4f1,stroke:#b3261e,stroke-dasharray:6 3,color:#8a8796;
    classDef undecided stroke-dasharray:2 2;
    classDef overruled fill:#f3f4f1,stroke:#c9ccc6,color:#8a8796;
    ST(["ST: Thomas Aquinas, Summa Theologiae, I,<br/>q.2, a.3"]):::axiom
    Ps102(["Ps102: Psalms 102:25-27"]):::axiom
    Heb1(["Heb1: Hebrews 1:3"]):::axiom
    P1["<b>P1</b>: Some things in the world are in motion.<br/><i>∃x. Moved(x)</i>"]:::premise
    P2["<b>P2</b>: Whatever is moved is moved by something<br/>other than itself.<br/><i>∀x. Moved(x) → (∃y. Moves(y, x) ∧ y ≠<br/>x)</i>"]:::premise
    P3["<b>P3</b>: An infinite regress of movers is<br/>impossible.<br/><i>¬Regress</i>"]:::premise
    P4["<b>P4</b>: If something is moved, every moved thing<br/>has another mover, and every mover is<br/>itself moved, then there is an infinite<br/>regress of movers.<br/><i>(∃x. Moved(x)) ∧ (∀x. Moved(x) → (∃y.<br/>Moves(y, x) ∧ y ≠ x)) ∧ (∀x. ∀y.<br/>Moved(x) ∧ Moves(y, x) → Moved(y)) →<br/>Regress</i>"]:::premise
    P5["<b>P5</b>: A first mover, itself unmoved, is what<br/>everyone understands to be God.<br/><i>∀y. ¬Moved(y) ∧ (∃x. Moves(y, x)) →<br/>God(y)</i>"]:::premise
    D1["<b>D1</b>: Therefore there is a first mover, moved<br/>by no other.<br/><i>∃y. ¬Moved(y) ∧ (∃x. Moves(y, x))</i>"]:::deduction
    C1["<b>C1</b>: Therefore God exists.<br/><i>∃y. God(y)</i>"]:::conclusion
    ST -.-> P1
    ST -.-> P2
    ST -.-> P3
    ST -.-> P4
    ST -.-> P5
    Ps102 -.-> P5
    Heb1 -.-> P5
    P1 --> D1
    P2 --> D1
    P3 --> D1
    P4 --> D1
    D1 --> C1
    P5 --> C1

Sources

ST

Thomas Aquinas, Summa Theologiae, I, q.2, a.3

Ps102

Psalms 102:25-27 (protestant canon)

Heb1

Hebrews 1:3 (protestant canon)

The argument