94. The First Way: Motion and the Unmoved Mover

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Lecture Notes

Main Topics #

• The Problem of Demonstrating Motion: The argument for God from motion requires proving two premises, neither of which is immediately obvious
• Self-Motion and Divisibility: Everything in motion is divisible; a thing cannot be the source of its own motion if parts of it are at rest
• The Infinite Regress Problem: Whether a chain of moved movers can extend infinitely or must terminate in an unmoved mover
• The Structure of the Argument: The first argument proceeds through disjunctive reasoning (either/or) to force acceptance of the conclusion
• Formal Logic vs. Material Truth: While the logical form may be simple, the real difficulty lies in proving the material premises true

Key Arguments #

The First Argument Structure #

• Everything that is in motion is moved by another (evident to the senses; requires proof)
• Either a mover is itself unmoved, or it is moved by another
• If moved, either this chain continues forever or terminates in an unmoved mover
• An infinite series of moved movers cannot actually move anything
• Therefore, there must be an unmoved mover (God)

First Premise: Everything in Motion is Moved by Another #

Proof from Divisibility (based on Physics VI):

• If something moves itself, it must contain the source (ἀρχή) of its own motion
• It must be the first thing moved (πρῶτον κινούμενον) within itself
• Everything in motion is divisible and has parts
• If one part is at rest, the whole cannot be first in motion
• If one part is moved while another is at rest, the whole is not moved by itself but by the moving part
• Therefore, nothing can move itself; all motion requires an external mover

Key insight: Motion cannot “belong first” to a thing because motion is the actualization of potentiality, and a thing in motion is by definition in process of receiving actuality from something else.

Second Premise: No Infinite Regress in Movers and Moved #

• An infinite series of moved movers—where each depends on another for its causal power—cannot actually move anything
• If every mover is itself moved, there is no first mover from which motion originates
• All would be “middle movers” with nothing to initiate motion
• Therefore, the chain must terminate in an unmoved mover

Important distinction: This argument rejects infinite regress in a per se ordered series (where each member depends on the prior for its causal efficacy), not in a per accidens series (like father-son-grandson generations)

Important Definitions #

• Unmoved Mover (Movens Immobile): A cause of motion that is not itself in motion; completely immobile and free from change; this is what God is
• Moved Mover (Movens Motum): A thing that moves other things only insofar as it is itself being moved; a middle cause in a causal chain
• Motion (Motus): In the strict Aristotelian sense, the act (ἐνέργεια) of what exists in potency (δυνάμει) as such; requires divisibility and dependence on an external cause
• First Moved (Primum Motum): That which is moved and is the immediate subject of motion, not moved by reason of its parts
• First in Motion: The point at which something first begins to be in motion; motion cannot have this property because before any motion, something must already be in motion

Examples & Illustrations #

The Glass and Paper Example: Berquist uses the image of pushing paper with a glass to illustrate the kind of ordered causality at work—the glass moves the paper insofar as the glass itself is being moved. This is a per se ordered series, not a mere temporal sequence.

Divisibility and Rest: If you have a divisible thing in motion and one of its parts comes to rest, the whole cannot be “first” in motion. For example, if your leg is at rest but your arm is moving, you as a whole are not moving by yourself, but only the part that is moving.

The Continuous Line: Berquist discusses how a mathematically divisible line can be divided infinitely without contradiction, showing that Thomas and Aristotle do not reject infinite division (potential infinity). Rather, they reject an infinite series of moved movers existing all at once and all being moved simultaneously.

Questions Addressed #

Can something move itself?

• No, not in the strict sense. If a thing is in motion, it must have parts, and if all its parts are in motion, then none of them is at rest to initiate motion. The motion must come from outside.

Why can’t the chain of movers go on forever?

• Because an infinite series of moved movers would have no first mover, and thus nothing would actually be moved. You cannot have an infinite chain of instruments being used with no principal user.

What does “first in motion” mean?

• It means the primary subject that is in motion, not moved by reason of its parts. Motion cannot belong “first” to anything because before something can be in motion, it must already have some motion—there is no actual beginning point of motion, only the dependence on an external mover.

Why is formal logic not the chief difficulty in this proof?

• While the logical structure (disjunctive syllogism) is straightforward, the real challenge lies in proving the material premises—that everything in motion is moved by another and that infinite regress is impossible. These require detailed analysis of the nature of motion and causality.

Structural Analysis of the Argument #

Berquist notes that there are really multiple syllogisms at work:

1. The Main Either/Or Syllogism: Either the mover is unmoved or it is moved (exhaustive disjunction); if unmoved, conclusion is reached; if moved, proceed to next syllogism.

2. The Regress Syllogism: If the mover is itself moved, either the series continues forever or terminates in an unmoved mover; it cannot continue forever; therefore it must terminate.

3. The Proof that Regress is Impossible: This requires backing up the conditional premises through detailed analysis based on the nature of divisibility and causality.

The formal logic is simple, but establishing the premises requires careful philosophical work grounded in Physics VI and VII.