33. Dialectical Reasoning and the Three Principles of Change

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Lecture Notes

Main Topics #

The Three Principles of Change #

• Aristotle argues that exactly three principles are necessary and sufficient for change: two contraries and a subject underlying them
• The first argument (presented as most necessary): change would be impossible without a third thing, since contraries cannot directly transform into each other
• The second and third arguments reason from the distinction between substance and accident: contraries exist only in accidents, not in substance; therefore substance must be a third principle

The Apparent Contradiction in Aristotle’s Reasoning #

• The Problem: Aristotle argues that there is contrariety in substance (in the second and third arguments against unlimited multitude) but also argues there is no contrariety in substance, only in accidents (in the middle arguments for needing a third thing)
• The Resolution: Aristotle proceeds dialectically from probable opinions rather than demonstrative necessity
• The Distinction: There are contrary differences in substance (e.g., rational vs. irrational, living vs. non-living) but not contrary species in substance (e.g., man and stone are not contrary like virtue and vice are)
• Result: Both statements contain partial truth and are therefore probable, though not demonstratively certain

Dialectical vs. Demonstrative Reasoning #

• Demonstration: Requires knowing which half of a contradiction is true; the demonstrator takes the true half and discards the false one
• Dialectic: Works with probable statements; both sides of an apparent contradiction may contain probability if each contains an element of truth
• Principle: If one half of a contradiction is manifestly true or false, the other must be its opposite. If one half is merely probable, the other half must also contain some probability
• Application: A probable opinion need not be the whole truth; it requires only some element of truth

Why a Third Thing is Necessary #

• The Core Issue: Can love itself become hate? No—that would be a contradiction
• The Solution: There must be a subject (e.g., a heart) that can lose one quality (love) and acquire its contrary (hate)
• The Principle: Unless there is a real distinction between the subject and the qualities it possesses, change is impossible
• Example: A heart capable of loving and hating can cease to love and begin to hate; the heart itself remains while its dispositions change
• Theological Application: Since God is identical with His love, He cannot hate; scriptural references to God’s hatred are metaphorical

Key Arguments #

The Necessity of a Subject for Change #

• If only two contraries existed with no underlying subject, no change could occur
• Love and hate cannot directly become each other
• A third thing (the subject) must persist while contraries come and go
• Without this distinction, as in God’s case, change becomes impossible

The Problem of Contraries in Substance #

• In one argument: substance is one genus with only one pair of contraries (no more than one pair needed)
• In another argument: there are no contraries in substance at all, only in accidents
• Resolution: The first argument speaks of contrary species in substance; the second speaks of contrary differences
• Contraries exist in different ways in different categories

Why Two Principles Are Insufficient #

• Two contraries alone cannot explain change
• Without a subject to undergo change, the contraries would simply replace each other
• A subject must remain constant while qualities alternate

Important Definitions #

Contraries #

• Species that are furthest apart in the same genus
• Examples: virtue and vice (species of habit); white and black (species of color); living and non-living (differences in substance)
• There can only be one pair of contraries in any genus, though this pair can be understood at different levels

Contrary Differences vs. Contrary Species #

• Contrary Differences: Opposition in the constitutive principles of things (e.g., rational vs. irrational constituting different animals)
• Contrary Species: When two species themselves stand as opposites (e.g., virtue and vice as contrary habits)
• Substance has contrary differences but not contrary species; accidents have both

Probable Opinion #

• A statement that contains some element of truth but is not demonstratively certain
• Based on the opinions of all men, most men, or experts in a given field
• Both sides of an apparent contradiction can be probable if each captures partial truth
• Example: “Sense pleasure is the best thing in life” is probable (most men believe it) but incomplete (philosophers recognize higher goods)

Dialectical Reasoning #

• Proceeds from probable premises rather than necessary ones
• Explores apparent contradictions as a path toward truth
• Works with statements that have some probability on both sides
• Comes before demonstration in the order of learning

Examples & Illustrations #

Change of Dispositions #

• Food preferences: A child dislikes certain foods; later in life, comes to like them. Neither the dislike nor the like was the same thing as the child; something (a subject) persisted while preferences changed
• Emotional change: Sometimes hate turns into love or love into hate. The person remains; their emotional disposition changes

Historical Military Examples #

• MacArthur at Inchon: MacArthur made the right decision about the Inchon Landing without certain knowledge of success. He proceeded on a “hunch” rather than demonstrative certainty. He had a contingency plan if it failed
• Nixon in South America: Nixon had a premonition that led him to change his route, avoiding a bomb set for his original path. He had no certain knowledge of danger
• Kennedy’s motorcade: Kennedy made the wrong “guess” about riding in an open car

Distinction Between Knowledge and Right Opinion #

• The fork in the road: A man wanting to go to Boston can get there either by knowing which fork leads to Boston or by having a right opinion about which fork leads there. Both reach the destination, but knowledge and opinion are different
• The point: Directing oneself to the good does not require knowledge; right opinion suffices

Questions Addressed #

How can Aristotle reason from both “there are contraries in substance” and “there are no contraries in substance”? #

• Answer: He is proceeding dialectically from probable opinions. There are contrary differences in substance (rational/irrational) but not contrary species in substance (man and stone are not contrary like virtue and vice). Both statements contain partial truth and are therefore probable rather than certain.

Why is the first argument for a third principle emphasized as more necessary? #

• Answer: Because it demonstrates that change itself is impossible without a subject underlying contraries. The second and third arguments depend on prior understanding of the substance-accident distinction, which is less immediately evident.

How does Aristotle’s hesitation at the end of the passage fit the overall argument? #

• Answer: His hesitation—uncertain whether there are two or three principles—reflects the dialectical nature of the inquiry. When proceeding from probable opinions rather than demonstrative necessity, apparent contradictions can arise that must be resolved through careful distinction rather than abandoned as incoherent.

Connections to Prior Concepts #

• Contradiction and Knowledge: Returns to the principle that contradictory statements cannot both be true and both be false; one must be true and one false
• The Role of Dialectic: Establishes dialectic as coming before demonstration in the order of learning, fitting the nature of the human mind which tends to see part of the truth before the whole truth
• Substance vs. Accident: Applies the fundamental distinction between what exists in itself (substance) and what exists in another (accident) to resolve the problem of change