1. The Structure and Order of Aristotle's Natural Philosophy

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Lecture Notes

Main Topics #

The Structure of Natural Philosophy #

• Aristotle’s natural philosophy proceeds methodologically from general to particular
• The eight books of natural hearing (Physics) establish principles of motion and change in general
• Three particular kinds of change are then distinguished in specialized studies
• This progression reflects an epistemological principle: universal principles are more certain and more known than particulars

The Three Kinds of Change and Modern Science #

• Change of place (local motion): Most general and presupposed to other changes; studied in De Caelo (books on the universe); corresponds to modern physics
• Change of sensible quality and substance: Studied in De Generatione et Corruptione; can lead to substantial change; corresponds to modern chemistry
• Change of quantity (growth): Particular to living things; presupposes qualitative change; corresponds to modern biology
• The order reflects increasing concretion (application to matter), not loss of generality

The Principle of Separation from Matter #

• All sciences are distinguished by their diverse ways of separation (or application) to matter
• Natural philosophy: Things whose definitions include sensible matter
• Mathematics: Things separated in definition but not in existence (quantity, shape without matter)
• Metaphysics/Wisdom: Things separated from matter in both being and definition
• There is no fourth possibility: something cannot be independent of matter yet defined with matter

The Organization of Aristotle’s Books on Living Things #

• First part: Three books De Anima (On the Soul)—considers the soul in relative abstraction from matter, not completely separated
• Second part: Intermediate books (De Sensu et Sensato, De Memoria, De Somno et Vigilia, etc.)—applies the soul’s powers to bodily organs and processes; ordered by the principle of proceeding from more immaterial to more material
• Third part: Books on particular animals and plants (History of Animals, Parts of Animals, Generation of Animals)—applies universal principles to specific species

The Four Grades of Living Things #

Aristotle distinguishes in the second book of De Anima:

1. Those with only the nourishing part of the soul (plants)
2. Those with sensation but no progressive motion (imperfect animals; e.g., clams)
3. Those with sensation and progressive motion from place to place (perfect animals; e.g., horse, cow)
4. Those with understanding (humans)

• The desiring power does not constitute a separate grade; it accompanies sensation (emotions) and understanding (will)

The Immateriality of the Intellect #

• The understanding is not the act of any part of the body (proven in book three of De Anima)
• Therefore, understanding cannot be studied by application to a bodily organ as other powers can be
• Its greatest abstraction lies in separated substances (angels); its greatest concretion remains in the soul
• Aristotle did not write a separate book on understanding and the understandable within natural philosophy; such study belongs to metaphysics

Thomas’s Ordering of the Intermediate Books #

Thomas proposes ordering the middle books by the principle per magis similia ad similia transire (to proceed from things more alike to things less alike):

1. De Sensu et Sensato (Sense and the Sensible)—sensation pertains more to the soul than to the body
2. De Somno et Vigilia (Sleep and Waking)—implies a gathering up or untying of the senses
3. Books on motive powers (locomotion)—more directed toward the body, less toward the soul
4. Books on life and death, youth and age, health and sickness—common considerations of life most applied to the body

Key Arguments #

The Epistemological Order of Natural Philosophy #

• Nature is defined by motion and change
• Since universal principles are more certain and more known than particulars, Aristotle first establishes principles of motion in general (Physics)
• Only then does he descend to particular kinds of motion and their corresponding sciences
• This order reflects how the mind naturally acquires knowledge: from confused universal impressions to distinct particular knowledge

Place as Gateway to Understanding the Universe #

• Change of place is the most general kind of change observable in nature
• Place is fundamentally determined in relation to the universe as a whole
• Therefore, the study of local motion necessarily leads to consideration of the universe as the ultimate place
• To specify where something is, one must eventually reference its place in the whole cosmic order

The Logical Order of the Three Sciences #

• Change of place presupposes nothing but motion itself
• Change of quality presupposes nothing but motion and quality; does not require life (occurs in non-living things)
• Growth (change of quantity in the vital sense) presupposes that food be qualitatively changed and transformed into one’s own substance; thus presupposes qualitative change
• Therefore, the order physics → chemistry → biology reflects an order of logical dependence among the phenomena studied

The Principle of Abstraction and Concretion in Natural Science #

• Just as natural science as a whole proceeds from the universal (motion in general) to the particular (specific sciences), within each science particular parts are distinguished by degree of separation from matter
• Universals are more separated from matter than particulars
• Therefore, within natural science, one should proceed from more universal to less universal considerations
• The De Anima considers the soul in relative abstraction; intermediate books apply it to bodily organs and processes; particular books apply it to specific species

Important Definitions #

• Nature (Natura): Defined fundamentally by motion or change; a principle of motion and rest within a thing
• Motion/Change (Motus): Includes local motion (change of place), qualitative change (change of sensible quality), and quantitative change (growth)
• Concretion/Application (Concretio): The application of universal principles to material or particular things; a diverse way of being applied to matter
• Abstraction (Abstractio): Consideration of something apart from matter, though not in complete separation; a relative abstraction
• Separation from matter: The degree to which a thing’s definition and being are independent of material conditions; distinguishes the three main sciences
• Substantial change: Change affecting the very substance or essence of a thing (often resulting from prolonged qualitative change)
• De Caelo (lit. “On the Heavens” or “Concerning the Universe”): Aristotle’s book on local motion and the structure of the cosmos; sometimes called T’Chelo or De Mundo
• De Sensu et Sensato (On Sense and the Sensible): Aristotle’s treatise on sensation and sensory organs; part of the intermediate group of books on living things

Examples & Illustrations #

Change of Place vs. Sensible Quality in Celestial Bodies #

• Aristotle observed that the sun, moon, and stars undergo change of place (daily and yearly motions) but appear not to change their sensible qualities
• This observation supports the principle that change of place is more general than change of quality
• In the sublunary realm, things can change place without changing quality, but change of quality typically requires things to be brought into the same place (contact)

Modern Division of Experimental Science #

• Physics corresponds to Aristotle’s study of local motion
• Chemistry corresponds to qualitative and substantial change
• Biology corresponds to growth and vital processes
• The modern experimental science division into “physical sciences” (combining physics and chemistry) and “life sciences” (biology) reflects Heisenberg’s organization by mathematical formalism rather than by type of change

Atomic Physics as Bridge Between Mechanics and Chemistry #

• Atomic physics belongs logically with mechanics (change of place) but modern practice sometimes associates it with chemistry
• This illustrates how the modern division by mathematical formalism can obscure Aristotle’s original division by type of change

Questions Addressed #

Why does Aristotle study motion and change in general before particular kinds of change? #

• Universal principles are more known and more certain than particulars
• The structure follows an epistemological principle: one should not require more experience than necessary
• Particular studies presuppose understanding of the general principles established in the Physics

How does place relate to understanding the universe as a whole? #

• Place is always determined relative to something larger
• A room is in a building, the building is on land, the land is in a state, and so on up to the whole universe
• The universe is the ultimate place, the final reference point for locating anything
• Therefore, study of local motion necessarily leads to consideration of the universe

Why is the intellect not studied in natural philosophy as other powers are? #

• The intellect is not the act of any bodily organ (proven in book three of De Anima)
• Other powers (nutrition, sensation, locomotion) can be studied both in the De Anima and through application to their bodily organs
• The intellect cannot be so studied; its consideration belongs to metaphysics, which treats separated substances
• Natural philosophy can demonstrate the intellect’s immateriality but cannot study it as a proper part of natural science

What principle governs Thomas’s ordering of the intermediate books on living things? #

• The principle per magis similia ad similia transire: proceed from things more similar to things less similar
• More similar to the soul’s immaterial consideration: sensation
• Less similar, more applied to matter: locomotion and general life processes
• This order maintains continuity with the De Anima’s approach while descending through degrees of materialization

Why are there only three possible ways for a science to relate to matter? #

• A science studies either: (1) things dependent on matter and defined with matter; (2) things in the material world but defined without matter; or (3) things not dependent on matter in being or definition
• There cannot be a fourth: something independent of matter yet defined with matter would be incoherent (there would be no reason on the side of the thing or the understanding to use matter in its definition)

Notable Quotes #

“Nature is defined by motion, right? So, here he’s talking about motion or change in general.”

“Change of place seems to be more common than change of sensible quality… change of place is more general and presupposed to change of quality.”

“The place is determined in relation to the universe. The universe is, in a sense, the last place.”

“For each thing is understandable to the extent that it is separable from matter.”

“The understanding is not the act of any part of the body, as is proved in the third book about the soul. Whence it is not able to be considered by concretion or by application of the body or to some bodily organ.”

“And because it is necessary… to go from things that are more alike, right? To things that are more unlike. This seems to be reasonably the order of these books.”