BELIEFS AND PHYSICS:
SOME LESSONS FROM THE ANCIENT GREEKS
Robert C. Newman
Interdisciplinary Biblical Research
Institute
Biblical Theological Seminary
www.ibri.org
ABSTRACT
A
brief sketch of ancient Greek physics from Thales to Aristotle reveals a strong
interaction between metaphysical belief and the practice of physics. This interaction worked in both
directions, as metaphysical views suggested (and inhibited) questions and approaches
to the physical realm, and physical observations and experiments favored or
disfavored various metaphysical views. Some lessons are suggested concerning how we should view
current theories in modern physics.
How
do metaphysical beliefs and physics interact? To formulate some answers to this question, we need to look
at actual examples. Here we
consider some of the earliest information we have on mankind seeking
systematic understanding of our physical environment. Work of this sort may have been done in
previous civilizations, but the first records we have come from the
Greeks, beginning with Thales of Miletus shortly after 600 BC. We will carry our survey down to
Aristotle in the fourth century BC, the first to attempt a comprehensive
physics.
From
our perspective at the end of the twentieth century, the physics of these
early scientist-philosophers seems crude, rash, and often absurd. Yet scientists only 200 years from now
may well think the same of our physics.
Let us, then, try to give each ancient thinker a sympathetic reading,
seeking to understand what forces led to each proposal, and how
physical observation and research affected metaphysical views and vice
versa.
There
are some advantages in picking examples from so long ago, in spite of
difficulties with historical sources.
These early researchers first proposed a number of fundamental
problems which have not been solved to this day. Yet we have advanced enough to see a good deal further along
the road than they could. We can,
perhaps, assess the fruit of their labors better than we can those of more
recent physicists.
The
Physical Substratum
How
do we explain the nature of the material world which we observe? This question was apparently first answered
in physical rather than supernatural terms by Thales of Miletus, a practical
thinker reputed to have made contributions to law, politics, civil
engineering, mathematics, and astronomy; he was even credited with successfully
predicting an eclipse of the sun in 585 BC (Nahm, 1964, pp. 32-33;
Farrington, 1949, p. 31).[1]
Thales proposed that there was a single basic substance behind all the
diverse phenomena we experience.[2] His rather tangible choice for
this substance was water. Thales
not only thought water was the substance on which the earth actually floated
(Aristotle, 325BCb, 2.13 [294a]),[3]
but also that it was the basis of all other materials. Aristotle (325BCa, 1.3 [983b]) suggests
he made this proposal because of the obvious necessity of moisture for
life. Nahm (1964, p. 33) thinks
perhaps it was because Thales knew that water could assume the three forms
C solid, liquid and vapor.
ThalesÕ
preference for natural causation, Farrington (1949, pp. 29-31) suggests,
came from observing various agricultural and industrial
techniques. He felt free to
advocate this openly because of the relative intellectual freedom in Melitus, a
city ruled at that time by merchants rather than a military or priestly
caste. Though preferring natural
causes, Thales does not appear to have been an atheist. Arisotle (325BCc, 1.5 [411a]) says he
thought Ôthat all things are full of gods.Õ Perhaps he realized that technological processes depend on
the natural attributes of the substances they manipulate, and this
led him to extend the idea to processes operating in nature. The proposal turned out to be a
fruitful one.
Anaximander
(fl 555 BC)[4] followed
Thales at Miletus, and was considered his student and successor (Theophrastus,
320BCb, 476). He also followed
ThalesÕ belief in a single natural universal substance, but rejected his
choice, water. Aristotle (325BCd,
3.5 [204b]; see also Lloyd [1970], p. 20) suggests he did this because he could
not see water as the source of fire, since their characteristics (cold and
wet vs. hot and dry) were mutually destructive. Anaximander proposed an abstract substance unlike
anything observed, which he called apeiron, meaning something like Ôunlimited,Õ Ôboundless,Õ or Ôinfinite.Õ This basic substance contained all
the opposites, and formed such secondary substances as fire and water by separation
(Aristotle, 325BCd, 3.5 [204b]; Simplicius, 530ADb, 32r). These secondary substances had their
origin in the apeiron
and returned to it when they were destroyed.
Anaximenes
(fl 535) was a third Milesian to investigate the basic constitution of
matter. He too favored a single
ultimate substance, but turned to an observable material, air, for his
choice. Perhaps he felt his predecessor's
apeiron was too far
removed from observation.[5] Anaximenes explained the diverse
observed materials as various manifestations of air. When rarefied, air becomes fire; condensed,
it forms successively wind, cloud, water, earth, and stone as the degree
of condensation increases (Hippolytus, 236AD, 1.6).
The
cosmologies the Milesians proposed were based on their physics. Thales had his earth floating on
water. Anaximander formed the
cold earth and fiery heavens by separation from the apeiron (Plutarch, 100ADb, 2). Anaximenes floated his earth on
air, and employed the wind to push his stars around (Hippolytus, 236AD, 1.6).
The history of Milesian views about the
primary substance is chiefly remarkable for the way in which the awareness
of the problems grew from one philosopher to the next. . . . As is usual in the history of science,
their actual theories strike a later age as childish C
they already appeared so to Aristotle.
But the measure of their achievement is the advance they made in
grasping the problems. They
rejected supernatural causation and appreciated that naturalistic explanations
can and should be given of a wide range of phenomena: and they took the first tentative steps towards an
understanding of the problem of change (Lloyd, 1970, pp 22-23).
A
Mathematical Substratum
A
different approach to the question of what underlies the physical world was
proposed by Pythagoras (fl 525), or possibly by one of his followers, the
Pythagoreans. Having observed that
harmonious sounds are produced by vibrating strings whose lengths have
simple ratios, he proposed that reality consists of numbers (Aristotle,
325BCa, 13.6 [1080b], 14.3 [1090a]).
Though the Pythagoreans apparently understood this in a rather crudely
literal sense, their suggestion led to increasing interest in the form
rather than the substance of matter.
This suggestion also proved fruitful for research from antiquity
onward, turning the attention of physicists and astronomers to
numerical measurement and mathematical modeling. It led to substantial advances in
knowledge among the Pythagorean astronomers. Unfortunately, it also produced a great deal of Ômumbo-jumbo
and crude number-mysticismÕ (Lloyd, 1970, p. 27).
Plato
(428-347) was influenced by the Pythagoreans, and counted knowledge of geometry
a necessity for admission to his Academy.
He observed that geometric drawings are at best only a rough
approximation to the ideas that lie behind them. For example, a true tangent meets its circle at one point
only, but it is impossible to draw this.
Plato apparently extrapolated this observation to reality in
general, coming to the conclusion that ultimate reality consists of eternal,
unchanging ideas, which are only imperfectly represented in the changing
world of objects observable by our senses. True knowledge is knowledge of these eternal ideas rather
than of unreliable sensory data.
The results are described by Clagett (1963, p. 84):
We do not have to wait until medieval or
early modern times for the application of geometry to the investigation of
nature, for it began in both physics and astronomy in the fourth century
[BC] and matured in the Hellenistic and Greco-Roman periods. We have already suggested the basic
importance of the Pythagorean mathematical point of view of nature; but
when the mathematical view was coupled with something close to scorn of the
world of the senses, as it was in some of the Platonic dialogues, little sound
physics could arise. Even the most
apologetic Platonist will not stand behind Plato's Timaeus as a work of high scientific caliber,
although it is true that some of the ideas suggested therein were not
without their influence on Aristotle and later authors.
Motion
and Vacuum
Meanwhile,
the question of how motion could be reconciled with the idea of a single,
universal substance was being considered by Parmenides (fl 480). He came to the rather startling
conclusion that it couldnÕt.
Parmenides believed the single universal substance to be being itself.
A vacuum was thus non-being, which by definition could not exist. Therefore all space was filled with the
single, ultimate substance which could not change without being
non-ultimate and which had no room to move (Parmenides, 480BCb). Rather than accepting the
testimony of human senses as indicating something must be wrong with
his argument, Parmenides chose instead to believe that our senses are
in error! (Parmenides, 480BCa).
ParmenidesÕ follower Zeno (fl 445) constructed several exceedingly
clever arguments to prove that motion did not exist. These arguments were frequently ignored but not successfully
refuted until the invention of calculus some 2000 years later.
One
solution to the quandary posed by Parmenides was to adopt a pluralistic
worldview rather than his monistic one C that there are several basic substances
rather than only one. In this
case, motion could take place as the different substances slipped by or mixed
with one another, even if there was no vacuum to provide extra room to move
about in. Empedocles (fl 445)
adopted this approach, proposing that there were four elements instead of
only one, namely earth, water, air and fire. All material things were a mixture of these, and change took
place when the composition of various mixtures changed. The cause of such change Empedocles
took to be two forces, which he called Love and Strife (we would call them
attraction and repulsion). This
model, as developed further by Plato and Aristotle, was to be the dominant
view in physics through the rest of antiquity until modern times (Clagett,
1963, p. 84).
Anaxagoras
(fl 445) carried the pluralistic idea to an extreme by postulating the
existence of an infinite number of different sorts of things C
Ôseeds,Õ or Ôgerms,Õ he called them C which are infinitely small and eternal. Every existing thing is a mixture
of these, so that when a human eats fruit (say), the body does not make flesh
and bone out of some other substance, but it extracts the flesh and bone particles
from the food (Anaxagoras, 445BC; Aristotle, 325BCd, 1.4 [187a-b]). AnaxagorasÕ influence does not appear
to have been great, as he was going against the preferred tendency to explain
the diversity of phenomena by as few items as possible. OccamÕs razor was already in use long
before Occam was born!
The
response to Parmenides which most neatly solved the problem he raised was the
atomic theory, proposed by Leucippus (fl 435), developed by Democritus (fl
410) (Simplicius, 530ADb, 28.15; Hippolytus, 236AD, 1.10-11), and
still further by Epicurus (341-270) (A‘tius, 100AD, 1.3.18; Cicero,
43BCa, 1.26.73). Reality,
said the Atomists, consists of an eternally-existing, universal
substance, but this occurs as an infinite number of unchangeable,
invisibly small particles, called ÔatomsÕ (indivisible) because they
could not be cut into smaller pieces.
The atoms were separated from one another by a void or vacuum, so
that motion was possible, and in fact, continual (Aristotle, 325BCd, 8.9
[265b]; Cicero, 43BCb, 1.6.17).
Unlike
AnaxagorasÕ seeds, atoms were all of the same substance, but differed
in size and shape. They formed the
various objects of our experience by collision and entanglement C
the origin of a particular material occurring when the atoms came
together, its destruction when the atoms separated. Thus change was real and didnÕt need to
be explained away as an illusion.
On the other hand, sensory characteristics themselves were due to the
shapes and combinations of the atoms, not to real colors and tastes in the
atoms. Democritus speculated
elaborately on the nature of sensory experience, and on how such
characteristics as hardness and softness, lightness and heaviness, were produced
in various objects (Simplicius, 530ADa, 293.33; Plutarch, 100ADa, 8;
Theophrastus, 320BCa, 6.1.6; Theophrastus, 320BCc, 49-82). Surprisingly, Democritus, too,
felt rational thought was more reliable than observation (Sextus
Empiricus, 200BC, 7.138).
The
ancient atomic theory never achieved dominance in antiquity like the modern
atomic theory has. It ascribed the
origin of the world to chance rather than intelligence, and it had nothing
beyond necessity to explain large-scale organization within the world
(Aristotle, 325BCd, 2.4 [196a-b]; Eusebius, 340AD, 14.27.4-5).[6]
The
Physics of Aristotle
By
the time of Aristotle (382-322), Greek astronomy had progressed to the point
that astronomical objects were obviously much larger and further away than
meteorological phenomena (Lloyd, 1970, p. 110; Farrington, 1949, pp.
99-100). Heraclides of PontusÕ (fl
330) proposal, that the daily movement of the sun, moon and stars was actually
due to the earthÕs rotation, may have come too late to influence Aristotle; it
did not meet with acceptance in any case (Clagett, 1963, p. 114; Sarton, 1964,
pp. 506-08; Lloyd, 1970, pp. 94-97).
Without telescopes, changes in the sky were not obvious beyond the moon,
so it is not surprising that Aristotle proposed a two-realm version of
physics. (1) Above the moon
was a supralunar realm without change, where all motion was eternal and
circular, following the scheme of Eudoxus (fl 365). (2) Below the moon was the sublunar realm of change,
characterized by natural vertical motion as each of the four elements sought
its own level (Clagett, 1963, pp. 84-87; Lloyd, 1970, pp. 109-10). Aristotle modified the four-element
scheme of Empedocles by allowing the elements to be transformed from
one into another, and by adding a fifth element, aether, from which the supralunar realm was
constructed (Clagett, 1963, pp. 85, 87; Lloyd, 1970, pp. 108-11).
Aristotle
also proposed four kinds of causation: (1) a material cause (like that of the
Milesians), what something was made of; (2) a formal cause (like that of the
Pythagoreans and Plato), how something was structured; (3) an efficient
cause (like that of Empedocles), what forces produced it; and (4) a final
cause, for what purpose the object was made (Farrington, 1949, pp. 123-24;
Clagett, 1963, pp. 84-85; Lloyd, 1970, pp. 105-06).
AristotleÕs
physics and causation continued to have influence through antiquity and
the medieval period until modern times, as they appeared to provide both
consistency and believable explanations for the observed natural order
(Clagett, 1963, p. 84; Lloyd, 1970, pp. 99, 122).
Interactions
Between Metaphysics and Physics
We
must now consider what we have learned about how metaphysical beliefs and
physics interact.
How
were physical concepts used to develop and evaluate metaphysical beliefs?
The
techniques of craftsmen may have suggested naturalistic explanations
for physical phenomena to Thales and his followers.
The
discovery that harmonious sounds were produced when vibrating strings had
lengths in simple ratios may have led the Pythagoreans to postulate the
idea that number is the ultimate feature of reality rather than matter.
The
realization that geometric drawings are at best only rough approximations to
the ideas that lie behind them apparently convinced Plato that ultimate reality
consisted of eternal ideas which are only imperfectly realized in physical
things.
Reluctance
to abandon sensory evidence kept many from following Parmenides, proposing
instead various models of reality in which change and motion were real. These included the multi-element
schemes of Empedocles and Anaxagoras, and the AtomistsÕ introduction of a
void and breaking the ultimate substance into tiny pieces.
Astronomical
evidence that the heavenly bodies were at great distances was in part
responsible (together with EudoxusÕ scheme for reducing the heavenly motions to
circles) for Aristotle's distinction between the earthly realm
of change and the changeless heavens.
How
were metaphysical beliefs used to develop and evaluate physical concepts and
theories?
The
MilesiansÕ metaphysic of natural causation led to their suggesting various
natural explanations for everyday phenomena which Greek mythology had
ascribed to Zeus, Poseidon, or one of the other gods. It also led to speculation regarding
a most basic substance. This
resulted, on the one hand, in beginning attempts to study the basis of matter;
on the other, it consistently produced (unwarranted) optimism that the
nature of the substratum could be easily discerned.
The
Pythagorean metaphysic of number as the basis of nature proved very fruitful in
some fields, and certainly was important in introducing mathematics as a tool
to understand reality.
However, it also led to considerable number-speculation where the
subject of investigation was not hospitable to such an approach at that time.
PlatoÕs
view that reality was in the eternal ideas, rather than in their imperfect
representations in nature, led him to devalue the use of observation and
experiment on physical objects in favor of purely abstract reasoning,
disconnecting theory from observation.
ParmenidesÕ
view that motion was logically impossible led him to reject the contrary
testimony of the senses.
DemocritusÕ
view that reality could be completely described by atoms moving in the void led
him to a number of striking insights, mixed with numerous unwarranted
speculations. His strongly
reductionistic explanations ignored the possibility of higher levels of structure
and of design in nature.
The
apparent completeness and consistency of AristotleÕs division of the
cosmos into two realms with two types of physics had long-term (and largely
negative) effects on the practice of physics, which were not overcome until the
late middle ages.
By
the time of Plato and Aristotle, widening class divisions in the Greek
city-states were discouraging the leisured class from involvement in hands-on,
technical sorts of labor. This
seems to have had a negative effect on any research which looked practical,
leading to the devaluation of the sort of physical investigations
which would later transform Western society in the centuries after the Reformation.
How
do shared metaphysical beliefs of the physics/science community influence
its research agenda?
There
were apparently no really organized physics or science communities at
the beginning of this era, but certainly the Milesians sought purely
natural explanations of phenomena.
Though this encouraged experimentation and observation, it
made it difficult for them to explain the occurrence of order in nature.
The
Pythagoreans were certainly a community, though more of a religious
fellowship than a scientific society.
They concentrated on applying mathematics to their investigations,
producing some impressive results where this was possible at the time
(astronomy and acoustics), but rather fantastic number-mysticism elsewhere.
The
Academy of Plato was mainly successful in its mathematical work, as the
emphasis on reason rather than observation tended to produce abstract, logical
constructions. PlatoÕs
proposal that the movement of astronomical objects be explained by combinations
of circular motions both helped and hindered astronomical research. Plato's admission of eternal forms gave
better explanations for order in nature than the merely material causation
of the Milesians and Atomists.
AristotleÕs
proposal of four types of causation (matter, structure, energy, and
purpose) made better sense of the observed order in nature. Together with a restoration of the
value of observation, this led to some effective biological research in the
Lyceum of his time and later.
Some
Lessons for Today
Can
such a brief tour of ancient Greek physics teach us anything about how we
should view physics today? I
believe it can. Consider the
following questions in the light of our survey.
Given
a hierarchical structure to reality, is there any reason to believe an
empirically constructed Ôbottom upÕ metaphysics will be anything more than
accidentally correct before the Ôfinal physicsÕ is discovered?
Ancient
Greek science, though showing real progress, does not seem promising for this
hope. ThalesÕ and AnaximenesÕ
proposals that water and air are the ultimate substances seem especially
crude to us, but they were based on certain observations. AnaximanderÕs more sophisticated idea
of an unspecified stuff behind appearances is an improvement, and it
sought to solve the problem of contrary attributes. AnaximenesÕ concept of condensation
and rarefaction, presumably based on the conversion of water into ice and
steam, also marked a step forward.
AristotleÕs version of EmpedoclesÕ four-element theory (earth,
water, air, fire), though returning to visible material as basic, at least
provided for one element to change into another. In retrospect, none of these suggestions were close to
what we know to be the case today.
Even
the ancient atomic theories, though a vast improvement with their
invisible units of structure and space between them, were unable to
explain macroscopic attributes except by arbitrary guesswork. Throughout the period we see increasing
sophistication, coupled with the incorporation of additional evidence,
which eventually was revived in modern times as a new atomic theory. But modern investigation has found that
what we call atoms are composites of nucleons and electrons, and that nucleons
are probably composites of quarks.
There is no way yet for us to tell if quarks, too, may not be
composite. We do not know how deep
the hierarchy is, nor whether anything lies beneath it.
How
does ÔOccam's RazorÕ influence physics?
Do we tend to jump to unwarranted conclusions about the
completeness of very preliminary theories?
Though
ÔOccam's razorÕ is a medieval term, it describes a common human tendency to
construct the simplest theory consistent with the known evidence; clearly,
it is valuable as a method of procedure.
But the ancient Greeks had no idea how complicated nature might be,
and tended to think they were only one layer away from the bottom. We can see they were mistaken,
having penetrated several more layers.
But what about our theories?
Are we only a layer away from the bottom of things, or do we also jump
to conclusions when we ascribe to them an ultimacy they may not deserve?
In
the area of kinematics, is it reasonable to believe nature can be limited to the
three spatial dimensions and one time dimension of modern relativity theory?
This
is certainly the simplest model consistent with our current, empirical, Ôbottom
upÕ physics. But mathematics
has been worked out for larger dimensionalities; some of the recent Ôgrand
unification theoriesÕ incorporate 11 or more dimensions; and certain
features of the occult and of the supernatural in Scripture point to
a more complex situation. OneÕs
worldview will have an influence on whether this is thought to be
possible or probable, and whether it might be worth pursuing as a research
strategy.
In
the area of dynamics, is it reasonable to believe that the four currently-known
forces are all that exist? That
they may be unified into a single superforce?
It
is certainly reasonable to believe these things in the sense that we know of no
reason why they might not be true.
The discussion above, however, should make us wary of too much confidence
here, since two of these forces (the strong and weak interactions) were only
discovered in the past century, and we have generally been poor prophets of
what advancing technology will turn up. The desire for unification and simplification has
often been fruitful in research, but like Pythagoreanism, has equally often led
astray.
In
the area of dynamics, is it reasonable to believe that knowing the ultimate
particles and physical forces will be sufficient to explain reality without
recourse to special initial or boundary conditions?
Without
making use of special revelation, we do not know the answer to this
question. However, the Ôfine-tuningÕ
in our universe, currently being discussed as the Ôanthropic principle,Õ
suggests that planning rather than chance is the more basic characteristic of
reality.
In
the area of dynamics, it is reasonable to believe that the universe is an
automaton (like a clock) that runs by itself C whether accidental or designed C
or may it be an instrument (like a guitar) that is designed for input?
Again,
input from special revelation is helpful here, though it is currently viewed as
Ômore scientificÕ to opt for a self-contained, closed universe.
After
some 2500 years of doing physics from inside our universe, we still donÕt know
whether there is an ultimate substratum, and if so, what it looks
like. We have progressed
enough to be sure it is not water, air, or atoms C in either the ancient or modern sense of
the word.
There
is a strange resonance in reality between mathematics in the human mind
and the structure of nature. We
don't know enough to say how pervasive this structure is or how it is imposed.
Parmenides
and Zeno were certainly mistaken about the unreality of motion. If it finally turns out they were right
about our senses being totally deceived, it will still have only been a lucky
guess. The human sensory apparatus
and its technological extensions have revealed an orderly world of much greater
complexity than any of the ancients imagined.
The
reductionism of Democritus is still with us in a suitably updated form,
but it faces some real challenges from design in nature. Aristotle was wrong about there being
two different kinds of physics for the terrestrial and astronomical realms. He might yet prove to be right for the
earthly and the heavenly.
BIBLIOGRAPHY
Most
of the items herein are ancient works.
For some of these, such as A‘tius and Sextus Empiricus, the dates given
are very approximate. For the
other ancient works, the date given is the author's date of death or floruit.
Dates before 1000 AD are marked AD or BC.
A‘tius. (100AD) Relics
of the Philosophers.
Anaxagoras. (445BC) Fragments.
Aristotle. (325BCa) Metaphysics.
Aristotle. (325BCb) On
the Heavens.
Aristotle. (325BCc) On
the Soul.
Aristotle. (325BCd) Physics.
Cicero. (43BCa) On
the Nature of the Gods.
Cicero. (43BCb) On
the Chief Good and Evil.
Clagett, Marshall. (1963) Greek Science in Antiquity.
New York: Collier.
Empedocles. (445BC) Fragments.
Eusebius. (340AD) Preparation
for the Gospel.
Farrington, Benjamin. (1949) Greek Science I: Thales to Aristotle.
Harmondsworth, Middlesex: Penguin.
Hippolytus. (236AD) Refutation
of All Heresies.
Lloyd, G. E. R. (1970) Early
Greek Science: Thales to Aristotle. New York: W. W. Norton.
Nahm, Milton C., ed. (1964) Selections from Early Greek Philosophy, 4th ed. Englewood Cliffs, NJ: Prentice-Hall.
Parmenides. (480BCa) The Way of Opinion.
Parmenides. (480BCb) The
Way of Truth.
Plutarch. (100ADa) Against
Colotes.
Plutarch. (100ADb) Miscellanies.
Sarton, George. (1964) A
History of Science: Ancient Science Through the Golden Age of Greece (New York: Wiley Science Editions.
Sextus Empiricus. (200BC) Against the Professors.
Simplicius. (530ADa) On
the Heavens.
Simplicius. (530ADb) Physics.
Theophrastus. (320BCa) Causes
of Plants.
Theophrastus. (320BCb) Doctrines
of Natural Philosophy.
Theophrastus. (320BCc) On Sense Perception.
[1]Some skepticism is
recommended about the eclipse story, given first in Herodotus Persian Wars 1.74. See Sarton
(1964, pp. 170-71).
[2]But see Lloyd (1970,
pp. 18-20), who thinks Thales was speaking of the origin of different sorts of
matter rather than their present composition.
[3]Most of the
Classical references in this paper can be found in Nahm (1964), though I have
translated his titles into English.
[4]Chronological data
on the various ancients comes from Lloyd (1970) or the Oxford Classical
Dictionary.