What is science?

Several views:

1) Behavior by which we gain control over the environment

2) Distinguish between

a) Science - Theoretical knowledge

b) Technology - Practical applications

This view needs more criteria to distinguish scientific from non-scientific theories. For this, see the following views.

3) Scientific theories defined by the form of their statements:

universal, lawlike statements, preferably equations. Ex.: Ideal gas law. Newton's 2nd law.

4) Define science by its method.

5) Define science by its epistemological status, what kind of justification its claims have.

6) Define science by its content.

7) Procedures or beliefs that are rigorous, precise, objective.

8) "Science" as a term of approval.

"Science" has several legitimate meanings.

'Science' has changed significantly over the centuries. Consequently the historian needs a very broad definition of "science" in order to properly understand the history of science.

"Natural philosophy" and "philosophy of nature":

Narrower than "scientia" and "episteme": Refers to the investigation of nature

Remember Isaac Newton's Mathematical Principles of Natural Philosophy. "Natural philosophy" later came to be called "natural science." Natural philosophy was viewed as a part of the larger quest to understand reality in general.

Prehistoric attitudes toward nature

Knowledge about nature has long been important to our survival.

But distinguish know-how from theoretical knowledge.

People can have practical rules of thumb without knowing the theoretical principles underlying them.

Primitive people transmitted knowledge orally, without writing. Characteristics of oral traditions:

They are fluid (changeable).

Cannot have historical archives or scientific reports.

Function is to justify current social structure and practices.

Primitive people have a different conception of explanations:

They anthropomorphize nature.

They seek individual causes, not causal generalizations.

They explain general features of the world in terms of more familiar processes.

Ex.: African myth about the earth being a mat that has been unrolled and remains tilted, thus explaining upstream and downstream.

Note: What is wrong with this explanation (aside from being generally false)?

General features of primitive world-view:

World divided into earth, sky, and sometimes underworld.

Deities are everywhere. No clear distinctions between human, nature, and supernature.

Belief in ghosts, spirits, and often in reincarnation

Magical rituals for controlling invisible powers.

Parochial conception of space & time.

Ex.: Cardinal directions as "upstream" & "downstream"

An African tribe, the Tio, cannot locate anybody farther than 2 generations in the past.

The present order is explained by its historical origins. History conceived as a series of isolated, decisive events.

Ex.: The story of the 9 Woots:

1. the ocean

2. the digger, who made riverbeds & hills

3. the flowing, who made rivers flow

4. who created the woods and savannas.

5. who created leaves

6. who created stones

7. the sculptor, who made people out of wooden balls

8. the inventor of prickly things

9. the sharpener, who made pointed things

Notice features of this 'explanation':

Anthropomorphization; everything explained by agents

Magical explanations. "Made people out of wooden balls"

Explanations of general features of the world are given in terms of individual, historical events.

The lack of system, lack of attempt at deeper explanations, and lack of ties to empirical evidence.

Human inventions attributed to deities.

Deities identified with physical objects like the ocean. Did they really think the ocean was a person? Cf. the Egyptian myth in which air and moisture give birth to earth and sky. Did they really think that air could have sex with moisture, that one of them could get pregnant, and that earth could come out of it like a baby?! Note the general lack of logic.

The healing arts connected with religion & magic. Witch doctors had both ordinary remedies & magical rituals for driving out spirits.

Primitive people have a different, or no conception of truth (?). Our criteria of truth:

Internal coherence

Correspondence with external reality

Their criterion:

"sanctioned belief". Community consensus.

How did the new conception of knowledge and truth originate:

Stages in the development of writing:

Pictograms: symbols stand for things

Logograms: Symbols stand for important words

Syllabic writing: symbols stand for syllables

Alphabetic writing: symbols stand for individual phonemes

Effects of the development of writing:

Puts stories into a permanent, visible form. Hence, makes possible inspection & comparison between different accounts.

This encourages criticism & the distinction between truth and myth or legend.

Enables people to make detailed lists, inventories.

This makes it possible to discover patterns in the information.

Writing thus led to the beginnings of science & philosophy.

( Other factors: The Greeks had contact with other cultures, including Egypt, the far East, the rest of Europe. This leads to a questioning, philosophical spirit.)

The beginnings of science in Egypt and Mesopotamia

Egyptian mathematics (circa 3000 B.C.):

Egyptians had a decimal number system.

They had geometrical formulae for calculating areas of simple figures and volumes of simple solids (e.g., triangle, rectangle, circle, pyramid)

They devised a simpler calendar, with 12 months of 30 days, plus 5 days at the end.

Mesopotamian mathematics (circa 2000 b.c.):

(Mesopotamia is the site of ancient Babylon & Assyria.)

Used a decimal and sexagesimal number system. Placement of symbols used to indicate powers of 60 (similar to our system, where placement indicates powers of 10).

Notice how this system differs from, say Roman numerals. Notice that this system enables one to write indefinitely large numbers with a limited number of symbols.

They also had generalized fractions.

They had techniques for solving what we would call algebra problems, e.g., given x*y and x+y, determine the values of x and y.

Babylonian astronomy:

Mapped some of the heavens, including prominent stars & constellations

Noted two kinds of celestial bodies: (a) the fixed stars, (b) the wandering stars, or planets (incl. sun & moon).

Identified the zodiac & divided it into 12 equal segments. The planets move through the zodiac.

Babylonian astronomers could predict motions of the planets, eclipses, and the appearance of the new moon.

Astronomy was also connected with astrology: the attempt to make predictions about human affairs, on the basis of the motions of the planets.

Egyptian & Mesopotamian medicine: it had 3 elements:

a) They believed diseases were caused by evil spirits. They had magical rituals for driving out the spirits

b) They also had medicines, and

c) They practiced surgery.

Note the beginnings of science. Their medical doctrine (though primitive) included careful observations of symptoms & cataloguing of ailments.


The world of Homer and Hesiod

The ancient Greeks credited Homer with writing:

The Iliad: The story of the Trojan War.

The Odyssey: The story of Odysseus' journey home after the Trojan War.

Hesiod wrote the Theogony: an account of the origin of the world and the gods. It describes the genealogy of the gods, and the major conflicts they underwent. Includes the overthrow of Kronos & the Titans by Zeus & the gods. Greek gods, together with their functions, include:

Zeus (the sky, weather, lightning, law & morality)

Hera (weddings & marriage; Zeus' wife)

Athena (war, protector of cities, wisdom)

Hades (underworld, the dead)

Ares (war)

Poseidon (the ocean, storms, earthquakes)

The gods are portrayed as taking an active role in human affairs. Nature was unpredictable, due to the possibility of divine whims.

Did people really believe these incredible, often nonsensical stories?

Compare: When people pray to God, thank God, do they really think God is intervening in their lives? In what way? Ex.:

An athlete asking God for a victory

Thanking God for your food at the dinner table

The first Greek philosophers

The first Greek philosophers (pre-Socratic) include: Thales, Pythagoras, Heraclitus, Anaximander.

Philosophy arose alongside mythology. But philosophy had distinguishing characteristics:

An attempt to understand nature rationally. Emphasis on argumentation.

Explanations appeal to the natures of things, not divine intervention. Explanations are sought in physical causes, rather than the motives of the gods.

Hence, nature is regarded as predictable, orderly, not capricious.

Note that this is the beginning of a scientific conception of causality.

The Milesians & the question of ultimate reality

The Milesians were a group of pre-Socratic philosophers from Miletus (in Ionia).

They held

materialism: the world is composed of physical material

monism: there is basically only one kind of stuff

Thales, famously, held that everything is composed of water.

The atomists (Leucippus, Democritus):

Everything is made of atoms (tiny, indivisible particles), moving around in the void. Their different configurations account for the differences in observed substances.

The theory of the 4 elements became popular later. The elements were earth, air, fire, and water.

Pythagoreans: followers of Pythagoras, who held that numbers were the most important, fundamental reality.

The problem of change

Heraclitus claimed that everything is constantly changing. It is impossible to step into the same river twice.

Parmenides argued that change is impossible. Why?

There are only two possible kinds of change: (a) being passing into non-being, (b) non-being passing into being.

Non-being can't exist (for then it would be being).

Therefore, (a) is impossible, for it would require non-being to exist at the later time.

Similarly, (b) is impossible.

Zeno says: Motion is impossible. 2 of Zeno's paradoxes:

(I) Imagine that you wanted to walk from point A to point B. In order to do so, you must first go ½ the distance. Then, you must go ½ the remaining distance (3/4 of the total distance), then ½ the remaining distance again, and so on. So:

1. In order to get to point B, you must complete the series (1/2, 3/4, 7/8, ...).

2. (1/2, 3/4, 7/8, ...) is an infinite series, which means it has no end.

3. An infinite series cannot be completed (for it has no end).

4. Therefore, you cannot complete the series (1/2, 3/4, 7/8, ...).

5. Therefore, you cannot get to point B.

(II) The race between Achilles and the tortoise. The tortoise gets a head start, but Achilles (assume) runs faster. When Achilles gets to the point where the tortoise started (point A), the tortoise has moved ahead a little bit (to point B). When Achilles gets to B, the tortoise has again moved ahead a little (to point C). Etc. Thus, Achilles must complete an infinite series in order to catch up to the tortoise. Therefore, he cannot catch up to the tortoise.

What about observations of motion, change??

Parmenides, Zeno say that the senses cannot be trusted. Change is only an illusion. We should trust reason over the senses.

The problem of knowledge

Parmenides & Zeno demonstrate epistemological concerns:

a) The attempt to provide an objective reason for one's conclusions. Notice how this differs from earlier, primitive thought.

b) The distinction between appearance and reality. The idea that things might be radically different from the way they appear.

c) The contrast between reason and the senses, and the preference given to the former.

Plato's world of forms

Relationship between Socrates & Plato: Plato was a student of Socrates. Plato wrote many dialogues in which Socrates figures.

Socrates died in 399 b.c. (executed, famously)

Plato divided reality into two realms:

a) The material world, concrete objects: perceived by the senses, changing, imperfect, somehow 'less real'. Like imitations of the Forms.

b) The Forms: Grasped by the intellect, unchanging, perfect, more real (whatever that means).

Arguments for the forms:

The 'one over many' argument: some classes of concrete objects have something in common. Like redness, beauty, tablehood. What is this 'something'? A Form (modern philosophical terminology: a "universal").

The imperfection of the material world: there are no (perfect) circles in the material world, but yet we have an idea of a (perfect) circle. What can this idea represent? The Form of circularity.

The allegory of the cave illustrates this doctrine.

Important epistemological points:

a) Again, Plato places intellect above the senses.

b) More importantly: he recognizes that what is important is what is universal, not what is particular. Compare this to modern science, which seeks explanations in terms of universal laws, and contrast with pre-scientific thinking. Scientists study universals (contrast history, which studies particular events).

Plato's cosmology

The world was created by a divine being, the Demiurge.

The Demiurge works with pre-existing materials with their own limitations

He acts according to a rational plan. This explains the order in the world.

The 5 regular solids are associated with elements:

Tetrahedron (4) -- Fire

Cube (6) -- Earth

Octahedron (8) -- Air

Dodecahedron (12) -- the cosmos as a whole (?)

Icosahedron (20) -- Water

Each element is composed of geometrical shapes.

Elements (except earth) can be transmuted by the recombination of their component triangles.

All observable substances are made of varying amounts of these 4 elements.

The world as a whole is a living thing, with a body and soul. The soul is responsible for all motion in the cosmos.

What Plato knew about the heavenly bodies. Different things you can see in the sky:

The fixed stars (almost all of the stars): these retain the same positions relative to each other. They're on a sphere (centering on the earth), rotating around the earth once a day.

The wandering stars (planets): Like the fixed stars, but they move relative to the fixed stars and each other. They always stay within a certain band of sky, though (the zodiac)

The sun: it moves in a certain band of sky (narrower than the zodiac, I think), called the ecliptic.

[Real reason: because the earth's axis of rotation is tilted.]

The achievement of early Greek philosophy

The ancient Greek philosopher/scientists discussed some of the same questions we investigate today (e.g., where did the world come from, what are the ultimate constituents of material objects, how is the cosmos arranged).

Other questions are largely forgotten, or relegated to 'philosophy' (how is change possible, how to balance reason vs. observation, how real are universals and particulars).

The latter are foundational questions, which they had to begin with. The Greeks laid the foundations for future investigation of nature, which we today take for granted.

[Is that really true? Exactly what are these foundations?]


Life and Works

Important life events:

Lived 384-322 B.C. (62 years) So he was young when Socrates died.

Studied with Plato for 20 years.

Tutored Alexander the Great.


Wrote major treatises on many areas of science & philosophy, including: logic, metaphysics, ethics, politics, aesthetics, physics, biology, and cosmology. Founded the science of logic.

Alas, most of his work has been lost.

Metaphysics & Epistemology

Rejects Plato's theory of Forms:

Particular things have independent reality.

Immanent realism: Universals exist only in particular things.

Matter & form always coexist in particular things:

Form: roughly, the collection of properties a thing has.

Matter: the substance (ultimate subject) which has those properties.

Holds an empiricist epistemology: All knowledge derives from experience.

1. First stage is sensory experiences.

2. Repeated experience yields memory.

3. By induction, one comes to grasp the essences of things, or universal definitions.

4. Scientific understanding is then completed when we see how to deduce particular aspects of observed things from their essences.

Did Aristotle employ this method in practice? Probably not.

[That's odd, isn't it? Couldn't he have observed himself in order to see how scientific thought actually proceeds?]

Nature & Change

In all change, there is something constant:

The matter remains

but it changes its form

Change is always between contraries (e.g. from hot to cold, or vice versa). It is between a form and its absence ('privation').

An answer to the Parmenidean challenge: Change is not merely a passing from non-being into being. Instead, there are 3 things:

a) Non-being

b) Potential being

c) Actual being.

Change is a transition from potentiality to actuality.

What causes change? The 'natures' of things. About natures:

Living things and the elements have natures. Artefacts do not.

The nature of an organism is not merely a summation of the natures of its constituents.

The nature of a thing is sort of like an inherent striving towards some end. Ex.: the element Earth has a natural place, which happens to be the center of the cosmos. That is why, if lifted away from that place, it strives to move back towards the center.

[Moliere made fun of this aspect of Aristotle's philosophy in his (Moliere's) play Le Malade Imaginaire. Asked why opium puts people to sleep, the Aristotelian doctor answers, "Because it possesses a virtus dormitiva" (Latin for "sleep-inducing power").]

The 4 causes:

Formal cause

Material cause

Efficient cause

Final cause

Aristotle's theory of nature is teleological: things behave in the way they do because of the end state they are innately tending towards. This idea is sort of taken up in modern biology, where one frequently hears about the functions of things.

[Things have functions or purposes. Note that this is not a psychological concept. Inanimate objects have functions according to Aristotle, which are inherent in their natures.]

Why Aristotle did not use controlled experiments: he thought that the nature of a thing would only be manifested in its natural circumstances. Artificial situations distort our evidence.


The elements: Earth, Air, Fire, & Water, plus a fifth element ("quintessence"), the aether. All other substances are mixtures of the first 4.

Fundamental properties: hot/cold, wet/dry

Earth: Cold & dry

Air: Hot & wet

Water: Cold & wet

Fire: Hot & dry

'Levity' of the elements (the contrary of weight) determine their natural positions. In order from heaviest to lightest:

Earth, Water, Air, Fire, Aether.

Heaviest elements tend towards the center of the cosmos; light elements towards the periphery.

Notice how this scheme explains: Earth sinks in water, so is heavier than it; air rises above water, so is lighter than it; Fire (flames) point upward, because fire is lighter than air.

Explains why the earth is spherical and at the center of the universe, and why it is surrounded by air.

The earth is surrounded by a concentric, spherical shell, the lunar sphere, which the moon is on, orbiting the earth. This divides the universe into 2 regions:

The terrestrial (sublunar) region, the region below the lunar shell: subject to generation, corruption [the contrary of generation].

The celestial region, that beyond the lunar shell: contains stars in unchanging patters of motion, amidst the aether. The celestial region is essentially changeless, uncorruptible.

The universe is a plenum (nature abhors a vacuum): all space is occupied.

That the ancients and medievals thought the Earth was flat is just a myth. Aristotle estimated the Earth's circumference, at about 1.8x the modern value. (De Caelo II.13) This may be the oldest recorded estimate.

Motion, Terrestrial & Celestial

All motion divides into 2 kinds:

Natural -- caused by a thing's nature

Forced -- caused by an external force (another object)

Motion is positively correlated with the motive force & inversely related to the resistance (thinner media resist less).

[Note: Forces are required to move things, not to change their state of motion as in Newton.]

Falling objects: speed is proportional to their weight (controlling for resistance).

Objection: Why do thrown objects continue in that direction after they leave your hand?

A: The medium (air) helps push them along.

[Notice that, at a first glance, this theory of motion corresponds to observation, and Newton's theory does not.]

Celestial motions:

The celestial sphere rotates around the earth once/day.

The fixed stars are fixed to the celestial sphere.

The sun moves on the celestial sphere around the ecliptic, once per year. Thus, it has its circular motion around the ecliptic superimposed on the daily rotation of the celestial sphere itself.

The moon moves on the same path, but making the circuit once per month.

Other planets have similar motions, but with occasional reverses.

[This is an elaborate system, accounting for the observed motions of the celestial bodies. Imagine the task of trying to account for those motions, without the benefit of a modern astronomy textbook. It's far from obvious that another system exists.]

Celestial bodies are moved by 'Prime Movers' or unmoved movers -- divine beings that the celestial objects strive to imitate. [People often refer to "the Prime Mover" in Aristotle, but note that there are more than one. Each body has its own.]

Aristotle as a Biologist

Aristotle collected lots of empirical data. He mentions over 500 different species, often describing them in meticulous detail. Witness his description of the development of chicken eggs. (And think about the observations required to obtain this information.)

The aim of these observations is to understand the causes of things.

Organisms (like everything) consist of matter and form.

Matter is supplied by the female, in reproduction. It is the material the organism is made of, including the various body parts.

Form is supplied by the male. It includes the way the matter is arranged; also includes the organism's final cause, the end towards which it strives. Form = soul: there are 3 kinds of soul:

1) The vegetative soul: responsible for nutrition & growth

2) The animal soul: responsible for perception & self-movement

3) The rational soul: responsible for thinking, reasoning.

Plants, animals, and humans are differentiated by the souls they possess.

[ Note that this is very different from the modern, Christian-inspired concept of "soul".]

Note: The soul is an aspect or attribute of the organism as a whole. Therefore, persistence of the soul after destruction of the body is logically impossible.

In growth, the organism moves from potentiality to actuality. The adult form is the final cause, the full 'actualization' of the organism. Particular events in the development are explained by the end it is aiming at.

Aristotle arranges living things in a hierarchy of superiority:

Prime Mover


viviparous animals (bearing live young)

oviparous animals (egg-laying)

vermiparous animals (bearing larvae)


This is supposedly related to the amount of 'vital heat' in living things. Related point: the lungs function to cool the organism.

[Can you think of empirical ways to test this theory?]

Aristotle's Achievement

[ Aristotle may have been the greatest thinker in history:

He wrote comprehensively, on all manner of subjects.

He put forward plausible theories that seemed to account for the observations, as well as studiously taking into account the opinions and arguments of his predecessors.

He single-handedly founded the science of logic, and wrote major works in many other disciplines.

In most cases, his theories became the accepted theories for centuries to follow.

Moreover, he integrated all of what he knew about the world into a single, coherent system. We see this in his application of the ideas of potentiality/actuality, matter/form, and the 4 causes to the different fields he investigated.

Note that Aristotle relies on arguments & observations, not on tradition or superstition. Also, what he can say at any given point is logically constrained by the rest of his system; unlike earlier, pre-scientific thought, which seems unconcerned about contradictions & arbitrariness.]