56. Defining Motion: Aristotle's Definition and Modern Errors

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Lecture Notes

Main Topics #

• The Definability of Motion: Whether motion can be defined, and how modern philosophers wrongly rejected this possibility
• Aristotle’s Definition of Motion: Understanding the precise formulation and its three essential components
• The Problem of Circular Definition: How to avoid defining motion through itself
• Motion as “Something of Another”: Why motion, like health, always belongs to something other than itself
• Act and Ability (δύναμις and ἐνέργεια): The foundational concepts needed to understand motion
• Incomplete vs. Complete Actualization: The distinction between partial acts that are on the way to further acts (motion) and partial acts that are not

Key Arguments #

Why Not Everything Can Be Defined #

• If every part of every definition needed to be defined, infinite regress would make all definition impossible
• Some things must be known without definition (like act itself)
• This principle applies equally to definitions, statements, and words
• Words learned: The first words cannot be learned through other words; they are learned by associating a sensed sound with a sensed object
• Aristotle recognized this principle long before Descartes and Locke, though they do not acknowledge it

The Circularity Problem #

• “Motion is the act of the movable” is true but circular (defines motion by itself)
• “Motion is the act of what is able to be in the room” (rather than “coming into the room”) avoids using the same word but is false
• The challenge: find a speech that is both true and non-circular

Motion as “Something of Another” #

• Motion never exists by itself; it is always the motion of something
• The falling stone is in motion, not the falling itself
• The walking man is in motion, not walking itself
• Therefore, motion is always “something of another,” like health is of the body
• This provides a multiplicity that can serve as the basis for a true definition

The Three Components of Aristotle’s Definition #

Motion is: “The act of what is able to be, insofar as it is able to be”

1. An Act (ἐνέργεια): Motion is an actualization of potential
2. An Imperfect Act: The ability is not fully actualized (e.g., when coming into the room, one is only partly in the room)
3. Ordered to Further Actualization: Motion is essentially on the way to a complete act; further actualization is essential, not accidental

The Critical Distinction: Motion vs. Partial States #

• Standing in the doorway checking IDs: Partly in the room, but it is accidental whether one ever goes further
• Coming through the doorway: Partly in the room, but it is essential that one will be further in if motion continues
• The Difference: Motion requires that further actualization is ordered to the nature of what is moving; a mere partial state does not

Important Definitions #

Motion (κίνησις) #

The act of what is able to be, insofar as it is able to be.

This captures: (1) actualization of potential, (2) incomplete actualization, (3) orientation toward further actualization.

Act (ἐνέργεια) #

• The realization or actualization of a potential
• Not itself definable, but foundational for defining motion
• Known without definition

Ability / Potentiality (δύναμις) #

• The capacity to be or do something
• Not yet actualized, but ordered to actualization

Movable (κινητόν) #

• That which is capable of being in motion
• Not itself motion, but the subject of motion

Examples & Illustrations #

Coming Into the Room #

• Outside the room: Able to be in the room, but not actually in it
• Coming through the doorway: Partly in the room; the ability is being actualized
• Fully inside: The ability is completely actualized (no longer motion)
• Standing in the doorway checking IDs: Partly in the room, but not essentially on the way further (accidental)
• Key distinction: Motion requires that further actualization is essential to it

Heating Water #

• Cold water: Able to be hot, but not actually hot
• Becoming hot: Some heat is actualized, but more will come (motion)
• Warm water (removed from heat): Partially hot, but no further actualization is essential (not motion)
• Boiling water: Fully hot (complete actualization, no longer motion)

Learning #

• Definition: The act of the ability to know (not the ability to learn, which would be circular)
• Student in class: Imperfectly knows, but will know more (motion toward knowledge)
• Student who drops out: Imperfectly knows, but is no longer learning (no essential orientation to further knowledge)
• The difference: Whether further actualization is ordered to the subject’s nature or merely accidental

Growing #

• Height is an example of motion from ability to act
• A person was once not actually 5'10" but was able to be, and is now actually 5'10"
• Growing is the motion by which this transition occurs

Notable Quotes #

“Motion is never the thing in motion. It’s not the falling that is falling, it’s a stone that’s falling. It’s not walking that goes for a walk, it’s the man that went for a walk.” — Berquist, illustrating that motion is always “something of another”

“Not everything can be defined, and not everything should be defined.” — Aristotle (cited by Berquist)

“The fact that we’re sure about motion might, if anything, be a sign that maybe we don’t know too clearly what it is.” — Berquist, responding to Descartes’ assumption

“They speak as if wisdom began with them… they speak as if… Aristotle hadn’t seen that.” — Berquist, on Descartes and Locke’s failure to acknowledge Aristotle’s prior insight

Questions Addressed #

Can Motion Be Defined? #

• Modern Answer (Descartes, Locke): No—motion is too simple/obvious to define
• Aristotelian Answer: Yes, through reference to act and ability
• Resolution: Understanding that not all things need be defined; act is known without definition, but motion can be defined in relation to act and ability

How Can We Define Motion Without Circularity? #

• Avoid using the same word (motion, moving, movable in the sense of actively moving)
• Instead, use “what is able to be” (the movable as potential)
• Add the qualifier “insofar as it is able to be” to distinguish motion from complete actualization

What Is the Essential Difference Between Motion and a Partial State? #

• Partial State: Imperfect actualization, but further actualization is accidental (may or may not happen)
• Motion: Imperfect actualization, but further actualization is essential and ordered to the nature of what moves (will happen as long as motion continues)

Why Do Modern Philosophers Fail to Define Motion? #

• They do not read Aristotle carefully enough
• They do not recognize that Aristotle already established the principle that not everything can be defined
• They overlook what Aristotle identified as undefined: act, not motion
• They fail to see that motion, being “something of another,” has the multiplicity necessary for definition