Mine is the first step and therefore a small one, though worked out
with much thought and hard labor. You, my readers or hearers of my
lectures, if you think I have done as much as can fairly be expected
of an initial start. . . will acknowledge what I have achieved and will
pardon what I have left for others to accomplish.
Aristotle
Aristotle
was born in Stagira in north Greece, the
son of Nichomachus, the court physician to the Macedonian royal
family. He was trained first in medicine, and then in 367 he was sent
to Athens to study philosophy with Plato. He stayed at Plato's Academy until
about 347. Though a brilliant pupil, Aristotle opposed some of Plato's
teachings, and when Plato died, Aristotle was not appointed head of
the Academy. After leaving Athens, Aristotle spent some time
traveling, and possibly studying biology, in Asia Minor (now Turkey) and its
islands. He returned to Macedonia in 338 to tutor Alexander the
Great; after Alexander conquered Athens, Aristotle returned to
Athens and set up a school of his own, known as the Lyceum. After
Alexander's death, Athens rebelled against Macedonian rule, and
Aristotle's political situation became precarious. To avoid being put
to death, he fled to the island of Euboea, where he died soon after.
Aristotle is said to have written 150 philosophical treatises. The 30
that survive touch on an enormous range of philosophical problems,
from biology and physics to morals to aesthetics to politics. Many,
however, are thought to be "lecture notes" instead of complete, polished
treatises, and a few may not be the work of Aristotle but of members of
his school.
A full description of Aristotle's contributons to science and philosophy is
beyond the scope of this exhibit, but a brief summary can be made:
Whereas Aristotle's teacher Plato had located ultimate reality in
Ideas or eternal forms, knowable only through reflection and reason,
Aristotle saw ultimate reality in physical objects, knowable through
experience. Objects, including organisms, were composed of a
potential, their matter, and of a reality, their form;
thus, a block of marble -- matter -- has the potential to assume whatever
form a sculptor gives it, and a seed or embryo has the potential to grow into
a living plant or animal form. In living creatures, the form was
identified with the soul; plants had the lowest kinds of souls, animals
had higher souls which could feel, and humans alone had rational,
reasoning souls. In turn, animals could be classified by their way of
life, their actions, or, most importantly, by their parts.
Though Aristotle's work in zoology was not without errors, it was the grandest
biological synthesis of the time, and remained the ultimate authority
for many centuries after his death. His observations on the anatomy of
octopus, cuttlefish, crustaceans, and many other marine invertebrates are
remarkably accurate, and could only have been made from first-hand experience
with dissection. Aristotle described the embryological development of a chick;
he distinguished whales and dolphins from fish; he described the
chambered stomachs of ruminants and the social organization of
bees; he noticed that some sharks give birth to live young -- his
books on animals are filled with such observations, some of which were not
confirmed until many centuries later.
Aristotle's classification of animals grouped together animals with similar
characters into genera (used in a much broader sense than present-day
biologists use the term) and then distinguished the species within
the genera. He divided the animals into two types: those with blood, and those
without blood (or at least without red blood). These distinctions correspond
closely to our distinction between vertebrates and invertebrates.
The blooded animals,
corresponding to the vertebrates, included five genera: viviparous quadrupeds (mammals),
birds, oviparous quadrupeds (reptiles and amphibians), fishes, and whales
(which Aristotle did not realize were mammals). The bloodless animals were
classified as cephalopods (such as the octopus); crustaceans; insects
(which included the spiders, scorpions, and centipedes, in addition to
what we now define as insects); shelled animals (such as most molluscs and
echinoderms);
and "zoophytes," or "plant-animals," which supposedly resembled plants
in their form -- such as most
cnidarians.
Aristotle's thoughts on earth sciences can be found in his treatise
Meteorology -- the word today means the study of weather, but Aristotle
used the word in a much broader sense, covering, as he put it,
"all the affections we may call common to air and water, and the kinds and
parts of the earth and the affections of its parts." Here he discusses
the nature of the earth and the oceans. He worked out the hydrologic cycle:
"Now the sun, moving as it does, sets up processes of change and becoming
and decay, and by its agency the finest and sweetest water is every day carried
up and is dissolved into vapour and rises to the upper region, where it
is condensed again by the cold and so returns to the earth." He discusses winds,
earthquakes (which he thought were caused by underground winds), thunder,
lightning, rainbows, and meteors, comets, and the Milky Way (which he thought
were atmospheric phenomena).
His model of Earth history contains some remarkably
modern-sounding ideas:
The same parts of the earth are not always moist or dry, but they change
according as rivers come into existence and dry up. And so the relation of land
to sea changes too and a place does not always remain land or sea
throughout all time, but where there was dry land there comes to be sea, and
where there is now sea, there one day comes to be dry land. But we must
suppose these changes to follow some order and cycle. The principle and
cause of these changes is that the interior of the earth grows and decays,
like the bodies of plants and animals. . . .
But the whole vital process of the earth takes place so gradually and in
periods of time which are so immense compared with the length of our life,
that these changes are not observed, and before their course can be recorded
from beginning to end whole nations perish and are destroyed.
Where Aristotle differed most sharply from medieval and modern thinkers was
in his belief that the universe had never had a beginning and would never
end; it was eternal. Change, to Aristotle, was cyclical: water, for instance,
might evaporate from the sea and rain down again, and rivers might come into
existence and then perish, but overall conditions would never change.
In the later Middle Ages, Aristotle's work was rediscovered and enthusiastically
adopted by medieval scholars. His followers called him
Ille Philosophus (The Philosopher), or "the master of them that know,"
and many accepted every word of his writings -- or at least every word that
did not contradict the Bible -- as eternal truth. Fused and
reconciled with Christian doctrine into a philosophical system known as
Scholasticism, Aristotelian philosophy became the official philosophy of
the Roman Catholic Church. As a result, some scientific discoveries in the
Middle Ages and Renaissance were criticized
simply because they were not found in Aristotle. It is
one of the ironies of the history of science that Aristotle's writings,
which in many cases were based on first-hand observation, were used to
impede observational science.
