Thomas Aquinas Thomas Aquinas Thomas Aquinas

12 Pages·2007·0.8 MB·English

Thomas Aquinas Thomas Aquinas
• Lived 1225-1274AD.
• The Catholic church came to prominence
around 500AD—1500AD.
• Christianity was the dominant religion.
• Aquinas was one of the greatest
interpreters of Aristotle’s work.
• He showed that Aristotle’s views could be
reconciled with Christianity.
The Scala Natura—The Great
Thomas Aquinas
Chain of Being
• In Aristotle we see a division amongst the • Pure Actuality (Prime Mover)
animals by way of the kind of soul they –Humans (Rational)
possess—nutritive, sensitive, rational. –Animals (Sensitive)
• This is a hierarchical ordering. –Plants (Nutritive)
• The ScalaNatura—The Great Chain of –Non-living natural objects (e.g. rocks, bone..)
Being. –The elements (earth, air, fire, water)
• Pure substance/Pure Potentiality
The Scala Natura—The Great
Chain of Being
• For Aquinas, things were ordered in the world
according to their perfection and reflecting God’s
plan.
• Humans are close to the top of the chain of
being, with God at the very top.
• Everything has a purpose (teleology)—God is
the Final Cause of all in the world.
• The Great Chain of Being reflects God’s plan.
• Thus, the Aristotelian world-view is consistent
with Christianity.
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Nicolas Copernicus (1473-1543)
The
Scientific
Revolution
Nicolas Copernicus Nicolas Copernicus
• Up until Copernicus’publication of On the • Copernicus revolutionized the way we
Revolutions of the Heavenly Bodies,the viewed the planetary system by proposing
Ptolemaic (90-168AD) model of the universe that the sun was the center of the (known)
was dominant theory. universe—heliocentric modelof the
• Ptolemy’s model was a detailed mathematical universe.
account of the orbits of the planets that was • This upset a great deal of traditional
geocentric (earth at the center). thinking.
• Aristotle presented a geocentric cosmology • Cosmology was tied to the notion of the
earlier than Ptolemy. Great Chain of Being.
Nicolas Copernicus Francis Bacon (1561-1626)
• The Earth was the focus of God’s creation an as
such was held to be the center universe—God’s
plan.
• As such his view was rejected by the Church.
• But it inaugurated an enormous shift in our
thinking about the world.
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Francis Bacon Francis Bacon
• Bacon ushered in a new way of thinking about how we • In the place of deduction, he argued for an
ought to go about understanding the world. inductive methodof inquiry.
• It was the first articulation of the scientific method—in his
• Scientific reasoning is still held to be a form of
NovumOrganon—a play on Aristotle’s Organon.
inductive reasoning.
• Bacon was deeply critical of the ancients and challenged
the fundamental form of reasoning they used in the • The goal was, through experience, to collect
acquisition of knowledge—the deductive method. facts in an unbiased way.
• He argued that there had been little progress to our • Then on the basis of an analysis of these facts
understanding of the world and that a reform was we proceed to make modest generalizations
required.
about the nature of the world—inductive
generalizations!
Francis Bacon Challenging Aristotelian Science
• In outline, this is an articulation of the • Aristotle’s explanation of change and motion were
basic tenets of the scientific method— informed by his cosmology.
observation, experimentation and • As a result of Copernicus’revolutionary changes
generalization. to the model of the universe, central portions of
Aristotle’s scientific system fell apart.
• During this period of scientific innovation,
Aristotle’s schema of matter and form also came
under challenge.
Challenging Aristotelian Science Challenging Aristotelian Science
• Critics argued that the claims became empty • Similar arguments can be presented against the
when applied to complex problems. definition of the soul.
• E.g. Aristotelians might say that sleeping powder • Recall, the soul is the form of living things.
achieves its result because it possesses “sleep • But the form is also that which makes something
qualities”—that which is potentiallyasleep the kind of thing it is.
becomes actuallyasleep in the presence of • Put these together and what Aristotle seems to
these qualities. be saying is that soul is that which brings life to
living things.
• But this doesn’t really help explain howthe
• All true…but not very helpful.
powder works.
• We want to know how the soul does this.
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Challenging Aristotelian Science Challenging Aristotelian Science
• Apart from these internal problems to the • Things move towards the full realization of
Aristotelian system, it also faced new respective forms and qualities.
challenges presented by a new approach • E.g. the acorn becomes an oak because it has
to science. the form built into it (its purpose/finalcauseis to
become an oak)
• Most significantly, the new science
• Similarly, the earth is “heavy”because its proper
rejected Aristotle’s explanations of cause
place is the centre of the cosmos, so it will
and effect.
naturally move there.
• Change for Aristotle was explained in • Similarly, fire moves upwards towards its natural
terms of things taking on forms and place in the outer regions.
qualities.
Challenging Aristotelian Science
Mechanical Explanations
• Thinking of causation in these purposeful ways
is to think in terms of teleological explanations
(ends, goals, purpose).
• Compare this with modern ideas of motion.
• Law of inertia: in the absence of external force
an object will maintain a constant state of rest or
uniform motion.
• Matter is inert—it has no natural direction of
motion, or internal drive.
Challenging Aristotelian Science Challenging Aristotelian Science
• In modern physics, motion is explained by • Part of the reason for this was the emptiness of
external forces acting on objects—which Aristotelian explanations.
will maintain there current state in the • There’s no point in explaining change in terms of
absence of such forces. goals etc., if the goal is just a re-description of
the change—we already know thatit changes,
• These are mechanical explanations.
we want to know why.
• A distinctive feature of the scientific • E.g. to explain falling objects by saying that they
revolution occurring in the 1600s was the naturally fall, isn’t much help.
rejection of teleological explanationfor • The forces proposed by mechanical
mechanical explanation. explanations seemed better suited.
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Challenging Aristotelian Science Challenging Aristotelian Science
Mathematical Laws • Platonic revival—the relationship between
• The new science also placed a great deal of mathematics and nature.
emphasis on mathematics as a tool for • As Aristotelian science became more
describing natural laws.
problematic, scholars in the middle ages
• Aristotle’s system was qualitative in nature— returned to this Platonic notion.
explaining change as changes in qualities—no
mathematics. • E.g. Copernicus on his heliocentric model…“we
find then in this arrangement an admirable
• A distinctive feature of the new science was the
formulation of mathematical laws and the harmony of the world, and a dependable,
replacement of qualitative descriptions with harmoniousinterconnection of the motion and
quantitative ones (time, weight, distance…). size of the paths, such as otherwise cannot be
• E.g. v = d/t discovered.”
Galileo Galilei (1564 – 1642) Galileo Galilei
• Galileo challenged the dominant Aristotelian
theory of motion with his detailed studies of the
times and motions of falling bodies.
• Famous canon-ball/musket-ball experiment at the
Tower of Pisa.
• Also performed various pendulum and rolling ball
experiments to show that Aristotelian theory of
motion was inconsistent with the observable
facts.
Galileo Galilei Galileo Galilei
• Galileo had adopted the new science and its • The Aristotelians said “that as he became a
mechanical and mathematical explanations to better mathematician he became a worse
explain motion. physicist, because he moved away from the
• As a result of his work, he faced increasing world as it appears in simple observations, and
criticism by the Aristotelians, who were, not focused instead on abstract and ideal
surprisingly on the side of the Church. mathematical descriptions of times and
motions.”
• In 1663 he was imprisoned by the Inquisition for
teaching Copernicus’theory.
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Challenging Aristotelian Science Challenging Aristotelian Science
(Again) (Again)
• This shift in thinking also did damage to • This led the new scientists to think that the real
Aristotelian confidence in the reliability of qualities of objects are not necessarily the ones
perception. we perceive.
• Thus, appearances (observation) may not be the
• Mathematical laws are idealizations of
ultimate guide to understanding the world—even
what we actually observe.
though it is the appearances we want explained.
• The acceptance of mathematical laws did • And this ushered in new challenges to Aristotle’s
not follow from their observability, but from account of the relation between the perceiving
the fact that they produced better mind and the physical world—that the real
predictions. qualities of objects are not like the sensations
we experience.
Galileo Again Galileo Again
An Argument Against Aristotelian Perception • If we run our hand over a statue, no one thinks
• Aristotle thought the qualities we perceive are the statue feels a tickle.
features of the objects of perception. • Thus, the tickling is not a property of the hand
• Galileo argues that this is a misattribution of (or feather).
things we know with our mind to the objects
• It exists solely in the mind of the person being
themselves.
tickled.
• Imagine being tickled lightly by a hand or a
feather. • The same goes for the other senses.
• Everyone agrees the tickling belongs to us and • Objects produce the sensation in us, but the do
not to the hand. Right? not possess sensation.
Galileo Again Galileo Again
• Galileo explained it instead as a result of the • For this and other reasons, Galileo thought
motion of particles of matter. that the only qualities that really exist in
• For example, he suggests that sensations of material objects are the sizes, shapes, and
sound are the result of moving air particles motions of the particles that cause
causing a vibration on the eardrum.
sensations.
• Differences in vibration (cid:198)differences in the
• Tastes, odours, sounds, are merely
sensation of sound in the mind.
sensations in our minds.
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Rene Descartes Rene Descartes
• Lived (1596-1650).
• Francis Bacon (1561-1626).
• Galileo Galilei(1564 –1642).
• Descartes was also an influential figure in
the new science.
• He was part scientist, part mathematician,
part philosopher.
Rene Descartes Rene Descartes
The Meditations • This was to be achieved by the systematic rejection of
• Descartes was obsessed with the idea that any assumptions that could possiblybe called into doubt.
scientific progress required that we have a • And on the basis of the foundation and reason alone
means of examining all beliefs—to separate (logic) we would secure (deduce) all knowledge.
those notions that are reliable from those that • Descartes was Rationalist.
are not. • How to doubt? Methodological Skepticism.
• In short, his goal was to find a secure foundation • There are two main arguments used to call all that we
for all of our knowledge. can into doubt.
• This is Descartes’Foundationalism.
(1) The Dreaming Argument.
• Like Galileo, he challenged the idea that
(2) The Deceiver Argument.
appearances should be the primary source of
information about the world.
Rene Descartes Rene Descartes
The Cogito • The one thing that seems difficult to doubt
• Given what has been set out in the previous
is that, there is some doubting going on.
arguments Descartes/the reader now has
grounds to doubt all his/her knowledge. • Cogito ergo sum: “I am thinking, therefore
• So where is this foundation that Descartes I exist.”
intended to find?
• All he needs (like Archimedes) is one point that • This is the foundational piece of
is “certain and unshakeable”to found his knowledge Descartes was looking for.
knowledge upon.
• But, we have already doubted everything…what
could possibly remain?
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From the Mind Onward From the Mind Onward
• What is a thinking thing? • What can we know about the external world?
• It doubts, understands, affirms, denies, is • Consider a piece of beeswax.
willing, imagines, perceives…but do all of • Examine its sensible qualities.
these attributes reallybelong to us? • Tastes like honey; Smells like flowers; has
distinct colour, shape, size…
• They are all merely kinds of thinking.
• Now place it near a fire.
• So, these ruminations support the idea
that the essence of the mind is thinking—it
is a thinking substance.
From the Mind Onward From the Mind Onward
• Once again, let’s examine its sensible • But we still see that the wax continues to
qualities. exist without them.
• The taste is gone; the smell is gone; the • These are merely accidentalfeatures of
colour and shape have changed, it’s larger the wax.
in size… • What we can say, at the very least, is that
• So what is essential to the wax? the wax takes up space—that it is
• It can’t be these sensible qualities since extended in general (it has extension).
they have all disappeared.
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From the Mind Onward From the Mind Onward
• How do we know this? • But Descartes realizes that he still can’t be
• The senses never give us a notion of certain of these claims.
general extension because all objects
• Thus, he ushers in (non-deceiving) God as
come with a particular shape, size etc.
a means of justifying these ideas.
• Extension is grasped by the understanding
• This is the antidote to the deceiver
not through our senses.
argument.
• So the essential feature of bodies is that
they are extended…and this we know via • I will leave aside the argument for the
the understanding. existence of God.
From the Mind Onward From the Mind Onward
• Once we accept that a non-deceiving God exists • Some of these clear and distinct ideas are
(since deception would be contrary to his
nature), then we can prove the certainty of our built into us—e.g. mathematical ideas.
knowledge.
• These are innate ideas: a perennial issue
• Thus, those ideas that are clear (i.e. vivid) and
in psychology.
distinct must also be true, for, if they were not,
God would be a deceiver.
• In this way, the existence of God validates many
of the ideas that we have.
• Thus, clear and distinct ideas cannot be
doubted, and they become our source of
knowledge.
Descartes’ Dualism Descartes’ Dualism
• So now we have two kinds of substances: 1. “The fact that I clearly and distinctly
thinking substances and extended understand one thing apart from another is
substances. enough to make me certain that the two things
are distinct.”…otherwise God is a deceiver.
• The essence of the mind is that it is a
2. I have a clear and distinct idea of myself as
thinking substance and the essence of
existing without a body…the essence of mind
material bodies is that they are extended is thought…the essence of body is extension.
in space.
3. Therefore, I am not my body (or God is a
• On the basis of this Descartes claims that deceiver).
the mind is distinct from the body— Mind and body are distinct! Platonism again.
mind/body dualism.
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Descartes’ Dualism Descartes Dualism
• Descartes thought that the pineal gland was • Gilbert Ryle(1949) referred Descartes view as the
“ghost in the machine.”
where the soul was located.
• As a result of these commitments we can also describe
• The reason for this was that all of the other parts Descartes as an interactionist—since the immaterial
of the brain are double. mind must be supposed to interact with a material body.
• This led to the Mind/Body problem that has been with us
• The pineal gland represented
since (Behaviourism/Cognitive Science).
was a single structure that could
• Descartes also assumed that we know things best
house the soul—a unitary object. through the understanding (mind), and thus the key to
knowledge was introspection.
• This became the foundation for later introspective
psychologists (William James).
Descartes and the Body Descartes and the Body
• Descartes also believed the mind to operate • The fire (A) displaces
according to its own rules, given by God, while the skin, which pulls a
the body is subject to mechanical laws. tiny thread (B), which
opens a pore in the
• Descartes conceived of the body as a kind of
ventricle (F) allowing
mechanical device (machine)—this was the "animal spirit" to
informed by some of the latest technological flow through a hollow
and scientific developments of the day. tube, which inflates
the muscle of the leg,
causing the foot to
withdraw.
Descartes and the Body Vaucanson’s Duck
• The development of various tinker toys
that mimicked animal actions were
inspiring (e.g. Vaucanson’sduck).
• This led to thinking of organisms as
machines and gave rise to the possibility
of building machines indistinguishable
from animals.
• This gave rise to the possibility of artificial
life, robotics, and artificial intelligence.
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