Aristoteles zu Galilei
Ulrich Leininger - firstname.lastname@example.org
Zur Zeit Galileis stand die etablierte Physik dem
kopernikanischen System entgegen. Für den Beweiß des
heliozentrischen Systems benötigte er eine neue Physik, die
die aristotelische Lehre verwerfen würde.
Erfahrung scheint der Bewegung der Erde zu widersprechen.
Diese vermeintliche Offensichtlichkeit musste Galilei zuerst
als Täuschung entlarven. In seinem Werk 'Dialog über die
beiden hauptsächlichen Weltsysteme' (Dialogo sopra i due
massimi sistemi del mondo, Tolemaico e Copernicano) versucht
er denn auch, durch verschiedene Beispiele den Leser zu überzeugen,
dass eine Bewegung, die nicht relativ zum Beobachter
stattfindet, sondern mit ihm, nicht wahrnehmbar ist. Im
wesentlichen unternimmt er dabei eine Übertragung der
irdischen Erfahrung in die kosmische Welt. Im Kleinen (z.B.
unter Deck auf einem fahrenden Schiff) sind Bewegungen des
Gesamtsystems nicht wahrnehmbar, also werden sie es auch im
Großen, d.h. bezogen auf die Erde, nicht sein.
damit die unmittelbare Anschauung auf ihre Ursache zurück.
Indem es ihm gelingt, die Anschauung als Folge von etwas
anderem zu erklären, nämlich der Unsichbarkeit
nicht-relativer Bewegungen, entkräftet er sie und hebt die
Vernunft auf den Thron der Wahrheit. Die Anschauung ist die
Wirkung eines Vorgangs, der sich nur vernunftmäßig begreifen
PHYSICS AND METAPHYSICS
Gordon L. Ziniewicz
Plato is a mathematician. Aristotle is a natural scientist
(his father was a surgeon). Plato's view is geometrical and
static (recall the importance of order for Plato). Aristotle's
view is biological and dynamic. In Greek, the word physis
means not just "nature," but "emergent
nature," "erupting nature." The image of
emerging nature is best depicted in the emergence of the oak
tree from the acorn. The living thing comes out of hiding, as
it were; it takes shape out of an indefinite and potential
source. Whereas in Plato we see the conscious forming of
unformed stuff according to a master blueprint, in Aristotle
we see the conscious or unconscious striving of natural beings
for self-realization, self-actualization, and self-fulfillment.
It is the urge for relative independence and complete life
that we see in Aristotle's picture of the universe.
there is only one world, the world of the particular things we
experience -- trees, horses, shoes, people, temples, etc.
There is no separate world of perfect (ideal) forms. There is
no ultimate heavenly blueprint of the perfect maple tree,
which all imperfect maple trees imitate; nor is there an
otherworldly blueprint of the perfect city or the perfect
human life. We must learn how to live in private or public,
not by reflecting upon a pure idea, but by observing and
understanding real just (more or less just) people and cities.
We do not arrange our lives in accordance with an ideal model;
we live our lives in imitation of the best actual citizens we
see around us. The real things that surround us -- those are
what we see and attempt to understand. To know what a maple
tree is in general is to look at a number of maple trees and
discover what they have in common. Aristotle is an empiricist,
not an idealist.
vision of nature is biological (life-centered) and
teleological (full of ends and purposes). The universe, for
Aristotle, is a series of layers, from the least developed and
least sophisticated beings to the most developed and most
sophisticated beings. It is a hierarchy that ascends a scale
from undeveloped potential matter (unformed stuff) to perfect
form (God). In order to understand these layers, we have to
appreciate that, for Aristotle, all the things we see around
us are changing.
always for Aristotle the actualization of some potential. What
can be changes to (becomes) what is. What previously lacked
form now possesses form (takes shape). A seed can become a
plant. An acorn changes -- that is, grows to become -- an oak.
A human being who can be a piano player but is not in fact a
piano player, changes into a piano player. An orangutan does
not have the potential to become a piano player; he cannot
change into a Chopin. Certain things have certain potentials;
a tulip bulb cannot become an oak tree.
What exists by
nature? Earth, water, air, fire (the four elements), plants,
animals, human beings, stars and planets, and God. Why do we
say these exist by nature? Because they all have within them
their own tendency to change, grow, etc. They have an innate
tendency to change; they themselves strive for their own ends.
Thus, all natural beings have natural inner inclinations,
desires, tendencies for fulfillment appropriate to their own
kind or species. Nature is dynamic. All natural things seek
fulfillment. They strive to live and to grow to maturity. They
seek their appropriate form. The child wants to become an
adult; the acorn wants to become an oak; the chick wants to
become a hen.
The degree of
life in anything is the degree to which it can bring about its
own fulfillment (its degree of autonomy, self-sufficiency, or
independence). The plant depends more upon its immediate
environment than animal or man does. For Aristotle, anything
has life to the extent that it contains its own principle of
change, its own life. Life exhibits self-movement and
God does not
create or rule, as Plato's demiurge (craftsman) and ruler-god
(providence). Aristotle's God does not know the universe
exists. He is eternally detached from particulars; he neither
produces nor governs. He has no friends, needs nothing outside
of himself. He is forever engaged in contemplation. His
thought is self-directed to the pure act of thought. He is
are not gods. They have minds - and bodies. The desire for
knowledge is the urge of the soul to imitate God as far as
possible, i.e. by enjoying knowledge of the order of the
universe. This knowledge is enjoyed for its own sake; that is,
it does not aim at some end outside of itself, such as
practical or political activity or any kind of production. It
is knowledge for its own sake. But because humans have bodies,
they have needs that can only be fulfilled in concert with
other bodies in the city. The soul is the life of the body.
The mind cannot pursue independent scientific contemplation
without the body being nourished by agricultural and
productive efforts, etc. Thus, the necessities of life must be
secured - one must have leisure - in order to pursue
To the modern reader, Aristotle's
views on astronomy, as presented in Metaphysics, Physics,
De Caelo (On the Heavens) and Simplicius' Commentary,
will most likely seem very bizarre, as they are based more on a
priori philosophical speculation than empirical
observation. Although Aristotle acknowledged the importance of
"scientific" astronomy - the study of the positions,
distances and motions of the stars - he nevertheless treated
astronomy in the abstract, linking it to his overall
philosophical world picture. As a result, the modern
distinction between physics and metaphysics is not present in
Aristotle, and in order to fully appreciate him we must try to
abandon this pre-conception.
argued that the universe is spherical and finite. Spherical,
because that is the most perfect shape; finite, because it has
a center, viz. the center of the earth, and a body with a
center cannot be infinite. He believed that the earth, too, is
a sphere. It is relatively small compared to the stars, and in
contrast to the celestial bodies, always at rest. For one of
his proofs of this latter point, he referred to an empirically
testable fact: if the earth were in motion, an observer on it
would see the fixed stars as moving, just as he now observes
the planets as moving, that is from a stationary earth.
However, since this is not the case, the earth must be at rest.
To prove that the earth is a sphere, he produced the argument
that all earthly substances move towards the center, and thus
would eventually have to form a sphere. He also used evidence
based on observation. If the earth were not spherical, lunar
eclipses would not show segments with a curved outline.
Furthermore, when one travels northward or southward, one does
not see the same stars at night, nor do they occupy the same
positions in the sky. (De Caelo, Book
II, chapter 14) That the celestial bodies must also be
spherical in shape, can be determined by observation. In the
case of the stars, Aristotle argued that they would have to be
spherical, as this shape, which is the most perfect, allows
them to retain their positions. (De Caelo, Book
II, chapter 11)
Wege zur Wissenschaftstheorie - Aristoteles
lebte 384-322 v. Chr. und ist neben Platon der fruchtbarste griechische
Philosoph. Er stammt aus einer angesehenen und wohlhabenden Arztfamilie
der makedonischen Stadt Stagira auf der Halbinsel Chalkidike und
erhielt die beste damals mögliche Ausbildung.
Aristoteles 17 jährig nach Athen,
um die vom damals schon 60 jährigen Platon
geleitete Wissenschafts- und Philosophieschule, die
Akademie, zu besuchen. Sie war zu dieser Zeit der Treffpunkt für
viele hervorragende Gelehrte aus allen Teilen Griechenlands.
die außerordentliche Begabung des jungen Aristoteles, dem man
in der Akademie bald den Spottnamen "der Leser" gab,
weil er Bücher nicht nur "hörte" (Bücher wurden
damals durch öffentlichen Vortrag vermittelt). sondern als
einer der ersten zum heute noch üblichen stillen Bücherlesen
weiterschritt und sich aus dem, was er las, eine große
Exzerptensammlung anlegte. 347, im Todesjahr Platons, verließ
der makedonenfreundliche Aristoteles das damals
antimakedonisch eingestellte Athen.