54. The Powers of the Soul and Locomotion

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Lecture Notes

Main Topics #

The Question of Locomotion #

• What power of the soul causes motion from place to place?
• This is distinct from growth, diminution, nutrition (shared with plants), and sensation (shared with immobile animals)
• Motion from one place to another requires both imagination and appetite

Critique of Inadequate Divisions of the Soul #

• Platonic three-part division: rational, spirited (θυμός/thumos), and desiring (ἐπιθυμία/epithumia)
• Makes sense in ethics but fails as complete account of soul’s powers
• Omits nutritive power (found in plants), imaginative power, and properly accounting for will
• Will (βούλησις/boulesis) should be grouped with other desiring powers, not treated separately with reason

The Two Motive Powers #

• Motion requires both desire (ὄρεξις/orexis) and practical reason working in harmony
• Theoretical reason (θεωρητική/theoretica) cannot move to action; it concerns truth only
• Practical reason (λογιστικόν/logisticon) is oriented toward doing/making and can move the soul
• These powers are unified in the desirable good (τὸ ὀρεκτόν/to orekton)—the appetible object that is both desired and reasoned about

Key Arguments #

Against the Nutritive Power as Cause of Locomotion #

• Plants possess nutritive power but do not move from place to place
• If nutritive power caused motion, nature would have provided plants with organs (legs, wings, fins)
• Nature does nothing in vain and lacks nothing necessary in complete, unmutilated creatures

Against Sensation Alone as Cause of Locomotion #

• Many complete animals have sensation but remain stationary (e.g., sea creatures attached to ocean floor)
• These are genuinely complete animals: they generate their own kind and have full growth and diminution
• If sensation caused motion, these animals would necessarily possess organs for locomotion

Against Theoretical Reason as Cause of Locomotion #

• Theoretical reason considers only truth, not what should be pursued or avoided
• Contemplating something fearful or pleasant does not automatically urge action
• Example: The heart may be moved while reason contemplates, but reason itself does not command the motion
• Theoretical reason is “very immobile”

The Unified Motive Principle #

• Neither reason nor desire alone causes motion; both must work together
• The desirable good (the end, the good) is the unifying principle
• Practical reason reasons backward from the desired end to present action
• Desire provides the motive force; practical reason provides the direction and method

Important Definitions #

Orexis (ὄρεξις) #

• Appetite or desire broadly; the genus of all desiring powers
• Includes: will (βούλησις/boulesis), sense desire (ἐπιθυμία/epithumia), and spirited appetite (θυμός/thumos)

Epithumia (ἐπιθυμία) #

• Sense desire; appetite for sensible pleasures and pains
• Distinguished from rational will by its object (sensible goods vs. rational goods)

Thumos (θυμός) #

• Spirited appetite; concerned with defending against difficulties or obstacles
• Related to courage and boldness; called the irascible appetite in Latin (appetitus irascibilis)

Logisticon (λογιστικόν) vs. Dianoia (διάνοια) #

• Logisticon: reasoning part; practical reason
• Dianoia: more general discursive thought
• Nus (νοῦς): understanding or intellect; grasps universal principles

To Orekton (τὸ ὀρεκτόν) #

• The appetible; the desirable good
• Serves as the starting principle (ἀρχή/arche) of practical reasoning
• What is both desired and the object of practical thought

Examples & Illustrations #

The Stationary Sea Creatures #

• Examples of complete animals with sensation but no locomotion
• Attached to ocean floor; water brings food to them
• Aristotle observed these as a marine biologist
• Proves that sensation alone cannot account for motion from place to place

The Cat Waiting for Birds #

• Berquist’s childhood observation of a cat sensing birds at a water source
• Cat hides in high plants, wiggles back and forth, then pounces
• Illustrates unified action of sense perception, desire, and motion
• Shows how imagination and appetite work together

Questions Addressed #

Which power of the soul causes locomotion? #

• Answer: Not the nutritive power (plants lack it despite having nutrition)
• Answer: Not sensation alone (stationary animals have sensation)
• Answer: Not theoretical reason (it does not orient toward action)
• Answer: Rather, a unity of desire and practical reason directed toward the desirable good

Why is the Platonic three-part division inadequate for natural philosophy? #

• Answer: It was designed for ethical discourse, not complete understanding of the soul
• Answer: It omits the nutritive power, the imaginative power, and misplaces the will
• Answer: It artificially separates will from other desiring powers

How do reason and desire work together in motion? #

• Answer: The desirable good (the end) is the unifying principle
• Answer: Practical reason reasons from this end backward to present action
• Answer: Desire provides the motive force toward that end

Methodological Notes #

• Aristotle recalls the adequate five-fold division of soul powers from Book II (nutritive, sensitive, imaginative, rational, locomotive)
• He uses dialectic in Chapter 9: raising problems that will be resolved after the chapter
• The inadequate divisions in ethics serve their purpose but must not be mistaken for complete philosophical account
• The relationship between imagination (φαντασία/phantasia) and appetite is crucial for understanding locomotion