17. Leucippus, Democritus, and Atomic Determinism

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Lecture Notes

Main Topics #

Leucippus and Determinism #

• Nothing happens at random: Leucippus states that everything comes to be “from reason or by reason and by necessity”
• Complete determinism: All events are necessarily determined; no element of chance exists
• Mathematical influence: Leucippus may have been influenced by mathematical science, where necessity (like the Pythagorean theorem in geometry) governs truth absolutely
• Principle of determinism in modern science: From the 17th through 19th centuries, determinism was considered the absolute principle of modern science
• Laplace’s formulation: If one knew the position and momentum of every particle in the universe at any moment, a sufficiently intelligent mind could predict the entire future course of history

Atomic Theory and the Thought Experiment #

• The atom (ἄτομος/atomos): Literally means “uncuttable” or “uncut”
  • Prefix A = negative (like “amoral,” “agnostic”)
  • Root -tomos = to cut
  • Aristotle’s account suggests not only “uncut” but “uncuttable”
• Democritus’s thought experiment: Imagine all bodies—including our own—cut in every possible way. What remains must be uncuttable things (atoms)
• Logical necessity of atoms: If bodies could be cut into nothing, they would be made of nothing, which is absurd. Therefore, something uncuttable must remain
• Nature of atoms: Have size and shape but cannot be further divided; may have size connected to their nature
• Modern clarification: Heisenberg noted that Democritus’s atoms are better compared to modern elementary particles, not modern atoms (which can be split by other means)

The Void (Kenon) #

• Necessity for change: Bodies cannot move unless there is empty space for them to move into
• Paradox: The void is literally nothing, yet “nothing” must exist for motion to occur
• Contrast with Empedocles: Empedocles rejected the void; Democritus accepted it to save the reality of change
• Willing contradiction: Democritus seemingly accepts the contradiction that “nothing is” in order to preserve the reality of becoming

Determinism in Modern Science #

• Claude Bernard (19th century physiologist): Wrote An Introduction to the Study of Experimental Medicine
  • Correctly identified that doubt is intrinsic to the experimental method
  • Yet excluded determinism itself from this doubt
  • Held that to doubt determinism would be to doubt science itself
• Einstein and confirmation: Even phenomenally accurate predictions (like Newton’s) do not prove a theory is true
  • Different hypotheses can predict the same phenomena
  • A scientific theory gains probability but never certainty through confirmation
  • Confirmation is not a valid syllogism
• Quantum theory challenge: Heisenberg formulated the principle of indeterminism in the Copenhagen Interpretation (associated with Niels Bohr and others)
  • Marked a shock to physics by rejecting classical determinism
  • Solvay Congress (1927): Einstein presented thought experiments to defend determinism; Bohr refuted them
  • Einstein’s final objection overlooked applications of relativity theory itself
  • Even if Heisenberg is right, determinism was the absolute principle of science for 300 years

The Problem of Change and Potency #

• Historical spiral, not circle: Return to similar concepts at different levels of experience
  • Ancient Greeks: recognized only change of place initially
  • Modern science: classical physics thought change of place was the only change
  • Quantum theory: forced recognition of other kinds of change
• Aristotle’s response: Will address this in Book VI and Book IX of Wisdom; uses understanding of potency (δύναμις) to explain becoming without contradiction
• Heisenberg’s connection: Modern quantum theory introduced a version of Aristotelian potency

Democritus on Ethics and Nature #

• On procreation: Do not generate children (you don’t know what you’ll get); adopt instead
  • Similar to modern concept of “designer babies”
  • Rationalist perspective contrasting with “let God decide”
• On understanding: “Don’t try to understand everything, lest you become ignorant of everything”
  • Relevant warning to modern attempts at total knowledge
• Sense qualities: “Sweet exists by custom, the bitter by custom, the warm by custom, the cold by custom, color by custom”
  • None of these truly exist in reality
  • Only atoms and the void truly exist
  • Influence of mathematical thinking: mathematics has no sense qualities, no substance, no purpose

Democritus on Man as Microcosm #

• Man is a little cosmos (μικρόκοσμος/microcosmos)
• Material and immaterial aspects: Humans have “a foot” in both worlds
  • Body: material
  • Understanding and will: immaterial
• Theological application: Explains appropriateness of God assuming human nature (man as image containing both material and immaterial)
• Knowledge as microcosm: Through sense, the soul takes on colors, sounds, and smells of all things; through understanding, it takes on the natures of all things
  • Aristotle’s teaching: “the soul is in some way all things”
• Scope of human knowledge: Cosmology shows man can take the whole universe into his mind

Man as Most Imitative of Animals #

• Imitation of nature: Humans imitate nature; art imitates nature; reason imitates nature
• Source in sensation: Knowledge begins with the senses; we sense things and then make something like them
• Example: Seeking shade under a tree when the sun is too bright demonstrates imitation of natural protection

Key Arguments #

The Atomic Argument #

1. Bodies can be imagined as cut in every possible direction and manner
2. Something must necessarily remain after all possible cutting
3. What remains is uncuttable by definition (ἄτομος)
4. Therefore, uncuttable atoms must exist as fundamental constituents
5. These atoms have size, shape, and position but cannot be further divided

The Void Argument #

1. Observable fact: Bodies change position and move
2. Motion requires space for bodies to move into
3. If nothing were empty, all things would be completely packed together (like sardines or clothes in a packed suitcase)
4. No motion would be possible in such conditions
5. Therefore, the void (empty space) must exist to allow motion

The Determinism Argument #

1. All events follow from prior causes by necessity (Leucippus)
2. Nothing occurs by chance or randomness
3. The future state of the universe is completely determined by the present state and causal laws
4. A sufficiently intelligent calculating mind could predict all future events (Laplace)
5. Therefore, absolute determinism governs all natural events

The Mathematical Influence Argument #

1. Leucippus and Democritus were influenced by mathematical study
2. In mathematics (geometry), necessity is absolute—the Pythagorean theorem cannot be otherwise
3. If one becomes accustomed to thinking of the world mathematically, one applies this necessity to all nature
4. Therefore, the deterministic principle follows naturally from mathematical training

Important Definitions #

Atom (ἄτομος/atomos) #

From Greek α- (a-, negation) + τέμνειν (temnein, to cut). Literally “uncuttable” or “uncut.” In Democritus’s theory, the smallest indivisible unit of matter that possesses size, shape, and position but cannot be further divided by any means. Aristotle’s account emphasizes not merely that atoms are “uncut” but that they are “uncuttable”—incapable of being divided.

The Void (κενόν/kenon) #

Empty space or nothingness that must exist alongside atoms for motion to be possible. Paradoxically, Democritus argues that “nothing” must “be” in order for change and motion to occur, accepting what seems to be a logical contradiction to preserve the reality of becoming.

Determinism #

The philosophical and scientific principle that all events are necessarily determined by prior causes according to natural laws, with no element of chance or randomness. Foundational to classical physics from the 17th through 19th centuries; challenged by quantum mechanics and Heisenberg’s principle of indeterminism.

Microcosm (μικρόκοσμος/microcosmos) #

Literally “little cosmos” or “little universe.” Applied to human nature: humans contain both material (body) and immaterial (soul, intellect) aspects, making them in a sense a universe in miniature. Through sensation and intellect, the human soul can come to know all things.

Confirmation (in scientific method) #

The apparent verification of a scientific hypothesis through successful prediction. Claude Bernard and Einstein clarify that confirmation does not prove a theory true by strict logical necessity; rather, it increases the probability of the hypothesis. The logical form is not a valid syllogism.

Examples & Illustrations #

The Thought Experiment of Cutting #

Democritus’s method: Imagine your body and every other body in the world subjected to cutting in every possible direction and manner. What could not be cut further would be the atoms. This thought experiment clarifies that something uncuttable must exist as a foundation for all physical things.

The Packed Suitcase Example #

Illustrates why the void must exist: If nothing were empty, all things would be packed completely tight, like clothes crammed into a suitcase so tightly that nothing could move. Since motion clearly occurs, empty space must exist.

Dreams and Determinism (Freud) #

Even phenomena that seem most random and irrational—dreams—are, according to Freud’s psychoanalytic theory, determined by unconscious causes. Berquist’s cousin’s dream of being chased by a tiger that suddenly asks “How would you like to buy a raffle ticket?” appears nonsensical, yet Freud would find deterministic causes. This demonstrates how determinism extends beyond physics into psychology.

Newtonian Physics vs. Einstein #

Newton’s physics was so phenomenally accurate in its predictions that 19th-century scientists began to think it must be the truth itself. When they observed planetary motions that didn’t match predictions, they hypothesized undiscovered planets rather than questioning Newton—and they were mathematically precise enough to predict where these planets were. Einstein later showed that different hypotheses (his relativity theories) could predict the same phenomena as Newton, plus additional phenomena. This demonstrates that confirmation increases probability but does not establish truth with certainty.

The Anecdote of Wine Tasting #

Berquist tasted a carbonate drink and found it sweet. But compared to other carbonates, it was “kind of sweet.” This illustrates that we name things by what they have most of, either absolutely or in comparison to other things. This principle applies to how we classify books (Psalms as a “book of prayer” though it contains prophecy; Macbeth as a “tragedy” though it contains comedy).

Notable Quotes #

“Nothing happens at random, but everything comes to be from reason or by reason and by necessity.” — Leucippus

“Sweet exists by custom, the bitter by custom, the warm by custom, the cold by custom, color by custom. None of these things really exist.” — Democritus

“Man is a little cosmos.” — Democritus

“Man is the most imitative of the animals, and he imitates nature.” — Democritus

“Don’t try to understand everything, lest you become ignorant of everything.” — Democritus

“A scientific theory is never known, in a strict sense, to be true. The more predictions you make, and the more exact they are, the greater probability for your hypothesis. But by the very form of the reasoning, it’s not a syllogism.” — Einstein (cited by Berquist)

“Doubt is intrinsic to the experimental method.” — Claude Bernard

“The position and momentum of every particle in the universe at any moment in time, if known, would allow a super-calculating mind to predict the whole future course of the history of the universe.” — Laplace (cited by Berquist)

Questions Addressed #

Why Does Determinism Seem Like the Absolute Principle of Modern Science? #

• Mathematical science (most rigorous) is deterministic by nature
• When other disciplines (biology, psychology) attempt to become “more scientific,” they adopt determinism as fundamental
• Claude Bernard excluded determinism from the doubt that properly applies to hypotheses, treating it as beyond question
• This held true from the 17th through 19th centuries until quantum mechanics

How Can We Reconcile Atomic Theory with Modern Physics? #

• Heisenberg notes that Democritus’s atoms should not be directly compared with modern atoms (which can be split by chemical and nuclear means)
• Better comparison: Democritus’s atoms correspond to modern elementary particles or whatever may be discovered as fundamental
• The principle remains: uncuttable (by current means) constituents of matter

Why Must the Void Exist? #

• For bodies to move and change position, there must be empty space into which they can move
• Without the void, everything would be packed absolutely tight with no possibility of motion
• Therefore, Democritus accepts “nothing” as something that exists

How Is Human Knowledge Related to Microcosm? #

• Through sensation, humans take on sensible qualities (colors, sounds, smells) of all things
• Through intellect, humans apprehend the natures of all things
• The human soul thus becomes, in a sense, all things—a universe in miniature
• This parallels Aristotle’s teaching in De Anima that “the soul is in some way all things”

Why Does Scientific Confirmation Not Prove Truth? #

• The logical form of confirmation is not a valid syllogism
• Different competing hypotheses can predict identical phenomena
• Multiple hypotheses may be compatible with the same data
• Therefore, confirmation only increases probability, never establishes certainty

How Does Quantum Mechanics Challenge Determinism? #

• Heisenberg’s principle of indeterminism emerged from quantum theory
• The Copenhagen Interpretation rejected classical determinism
• Even Einstein, at the 1927 Solvay Congress, attempted to defend determinism through thought experiments
• Bohr refuted Einstein’s objections, and Einstein never publicly challenged the rejection of determinism again