5. Common and Private Experience in Natural Philosophy

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Lecture Notes

Main Topics #

Common vs. Private Experience #

Common Experience

• Experience which all humans have and cannot avoid having
• Two-part definition: universality (all men have it) + necessity (cannot avoid it)
• Examples: pleasure and pain, whole and part
• Everyone experiences pleasure and pain in living; impossible to live without experiencing whole and part (breathing in whole air vs. part of air)

Private Experience

• Experience which only some humans have
• Can be acquired by: deliberate experiment, prolonged observation, exposure by chance, or special effort and tools
• Not necessarily avoidable (e.g., being hit by a car results in broken leg whether desired or not)
• Examples: giving birth (no man experiences this), having a female cat give birth (personal example of kittens returning to same nipple)

The Relationship to Natural Philosophy and Experimental Science #

Philosophy of Nature (narrow sense)

• Based exclusively on common experience
• Aristotle’s eight books on natural hearing (Physica) require only common experience
• Aristotle’s three books on the soul (De Anima) require only common experience
• No laboratory needed because students already have the requisite experience

Experimental Science

• Based on private experience
• Requires experience not everyone has
• Labs are provided to give students access to private experience not generally available
• Includes division of labor: some scientists are empirical (conduct experiments), others are theoretical (work with data to find order)

Why This Matters for Knowledge

• Knowledge based on common experience is more general than knowledge based on private experience
• This follows from the natural road principle: general knowledge comes before particular knowledge
• We can syllogize: if general comes before particular, then knowledge from common (more general) experience comes before knowledge from private (more particular) experience

Historical Context: Terminology #

• Natural Philosophy historically covered all study of the natural world (Sir Isaac Newton’s Principia Mathematica Naturalis Philosophiae)
• In Scotland, physics, chemistry, and biology departments are still called “natural philosophy”
• Modern usage distinguishes:
  • Natural philosophy = study based on common experience
  • Experimental science = study based on private experience
• This distinction reflects that some parts of natural philosophy require no private experience at all

Key Arguments #

Why Common Experience Suffices for Natural Philosophy #

1. The task of natural philosophy is not to extend our experience but to understand the experience we already have
2. We possess inward, common experience of motion, change, and life
3. This common experience is both universally available and unavoidable
4. Therefore, no special equipment or experiments are needed
5. This contrasts with experimental science, which aims to extend the range of our experience through specialized tools and methods

Distinction from General/Particular Knowledge #

• Do not confuse common/private experience with general/particular knowledge
• In geometry, knowledge that a triangle is a triangle (general) vs. an equilateral triangle (particular) comes from the same kind of experience
• The common/private distinction concerns the type of experience (universal and unavoidable vs. special and limited)
• The general/particular distinction concerns the level of universality of knowledge itself

Why Philosophy of Nature Doesn’t Require a Lab #

• Common misconception: “Why no lab for philosophy of nature if we study natural things?”
• Answer: The course is based on experience students already have and cannot avoid
• Physics, chemistry, biology courses have labs because they depend on private experience
• This reveals the fundamental nature of each discipline

Important Definitions #

Common Experience (experientia communis)

• Experience all humans have and cannot avoid having while living in the world
• Foundational to natural philosophy in the Aristotelian sense

Private Experience (experientia privata)

• Experience which only some humans have
• May be acquired by experiment, prolonged observation, chance exposure, or special effort and tools
• Foundational to experimental science

Philosophy of Nature (narrow sense)

• That part of the study of natural things based on common experience alone
• Distinguished from experimental science, which requires private experience
• Represents the original Greek natural philosophy as developed by Aristotle

Experimental Science

• Knowledge of the natural world based on private experience
• Characterized by division of labor between empirical and theoretical scientists
• Aims to extend the range of human experience and reduce it to order (Niels Bohr)

Examples & Illustrations #

The Female Cat and Kittens #

• Personal observation: daughter acquired a female cat that gave birth
• Daughter researched that each kitten goes to a different nipple (and same nipple consistently)
• Observation: watched one distinctively colored kitten always return to same nipple
• Significance: This is private experience (not all people have had female cats give birth) that gives knowledge beyond common experience
• Philosophical point: Nature avoids chaos through internal ordering when multiple animals (seven kittens) must feed from limited resources

Why No Laboratory for Philosophy of Nature #

• When students ask: “Did you register for a lab? Why isn’t there a lab like in physics or chemistry?”
• The answer reveals the fundamental difference: Philosophy of nature is based on experience you already have and cannot avoid
• Physics/chemistry labs exist because those sciences depend on private experience not everyone has
• This distinction clarifies the nature and scope of each discipline

Pleasure and Pain as Common Experience #

• Everyone experiences pleasure and pain
• No way to live in the world without having some experience of pleasure and pain
• Therefore, we can discuss pleasure and pain in general on the basis of common experience
• This generality contrasts with discussing particular pains (childbirth, broken leg, abscessed tooth) which require private experience

Notable Quotes #

“The task of science is both to extend the range of our experience and to reduce it into order.” - Niels Bohr

Berquist contrasts this with natural philosophy, which does not aim to extend experience but to understand common experience already possessed.

“In the case of the philosophy of nature, Aristotle’s not trying to reduce our experience to order, he’s trying to find order in the natural things.”

This captures the fundamental difference: experimental science imposes mathematical order on experience; natural philosophy discovers order already present in nature.

Questions Addressed #

Why don’t we need a laboratory for the philosophy of nature course? #

• The course is based on experience students already have and cannot avoid having
• Unlike physics or chemistry, which depend on private experience requiring special equipment, philosophy of nature draws from universal common experience
• No experiment is needed because everyone has already experienced motion, change, and life

How do common experience and general knowledge relate? #

• Knowledge based on common experience tends to be more general than knowledge based on private experience
• But these are distinct distinctions: common/private refers to the type of experience; general/particular refers to levels of universality in knowledge itself
• A geometric statement (even if general) does not depend on a distinction between common and private experience

Why does experimental science require both empirical and theoretical scientists? #

• Division of labor exists because private experience is not necessarily possessed by all scientists
• Empirical scientists conduct experiments to obtain private experience
• Theoretical scientists work to order this experience mathematically
• Example: Einstein did not conduct the Michelson-Morley experiment that helped prompt his theory of relativity
• Example: Einstein did not observe the solar eclipse experiments that confirmed general relativity; this was done by Sir Arthur Eddington’s team