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.
Thomas Aquinas
• In Aristotle we see a division amongst the
animals by way of the kind of soul they
possess—nutritive, sensitive, rational.
• This is a hierarchical ordering.
• The Scala Natura—The Great Chain of
Being.
The Scala Natura—The Great
Chain of Being
• Pure Actuality (Prime Mover)
– Humans (Rational)
– Animals (Sensitive)
– Plants (Nutritive)
– Non-living natural objects (e.g. rocks, bone..)
– 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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The
Scientific
Revolution
Nicolas Copernicus
• Up until Copernicus’ publication of On the
Revolutions of the Heavenly Bodies, the
Ptolemaic (90-168AD) model of the universe
was dominant theory.
• Ptolemy’s model was a detailed mathematical
account of the orbits of the planets that was
geocentric (earth at the center).
• Aristotle presented a geocentric cosmology
earlier than Ptolemy.
Nicolas Copernicus
Nicolas Copernicus (1473-1543)
Nicolas Copernicus
• Copernicus revolutionized the way we
viewed the planetary system by proposing
that the sun was the center of the (known)
universe—heliocentric model of the
universe.
• This upset a great deal of traditional
thinking.
• Cosmology was tied to the notion of the
Great Chain of Being.
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
• Bacon ushered in a new way of thinking about how we
ought to go about understanding the world.
• It was the first articulation of the scientific method—in his
Novum Organon—a play on Aristotle’s Organon.
• Bacon was deeply critical of the ancients and challenged
the fundamental form of reasoning they used in the
acquisition of knowledge—the deductive method.
• He argued that there had been little progress to our
understanding of the world and that a reform was
required.
Francis Bacon
Francis Bacon
• In the place of deduction, he argued for an
inductive method of inquiry.
• Scientific reasoning is still held to be a form of
inductive reasoning.
• The goal was, through experience, to collect
facts in an unbiased way.
• Then on the basis of an analysis of these facts
we proceed to make modest generalizations
about the nature of the world—inductive
generalizations!
Challenging Aristotelian Science
• In outline, this is an articulation of the
basic tenets of the scientific method—
observation, experimentation and
generalization.
• Aristotle’s explanation of change and motion were
informed by his cosmology.
• As a result of Copernicus’ revolutionary changes
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
when applied to complex problems.
• E.g. Aristotelians might say that sleeping powder
achieves its result because it possesses “sleep
qualities”—that which is potentially asleep
becomes actually asleep in the presence of
these qualities.
• But this doesn’t really help explain how the
powder works.
• Similar arguments can be presented against the
definition of the soul.
• Recall, the soul is the form of living things.
• But the form is also that which makes something
the kind of thing it is.
• Put these together and what Aristotle seems to
be saying is that soul is that which brings life to
living things.
• All true…but not very helpful.
• 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
Aristotelian system, it also faced new
challenges presented by a new approach
to science.
• Most significantly, the new science
rejected Aristotle’s explanations of cause
and effect.
• Change for Aristotle was explained in
terms of things taking on forms and
qualities.
• Things move towards the full realization of
respective forms and qualities.
• E.g. the acorn becomes an oak because it has
the form built into it (its purpose/final cause is to
become an oak)
• Similarly, the earth is “heavy” because its proper
place is the centre of the cosmos, so it will
naturally move there.
• Similarly, fire moves upwards towards its natural
place in the outer regions.
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
external forces acting on objects—which
will maintain there current state in the
absence of such forces.
• These are mechanical explanations.
• A distinctive feature of the scientific
revolution occurring in the 1600s was the
rejection of teleological explanation for
mechanical explanation.
• Part of the reason for this was the emptiness of
Aristotelian explanations.
• There’s no point in explaining change in terms of
goals etc., if the goal is just a re-description of
the change—we already know that it changes,
we want to know why.
• E.g. to explain falling objects by saying that they
naturally fall, isn’t much help.
• The forces proposed by mechanical
explanations seemed better suited.
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Challenging Aristotelian Science
Challenging Aristotelian Science
Mathematical Laws
• The new science also placed a great deal of
emphasis on mathematics as a tool for
describing natural laws.
• Aristotle’s system was qualitative in nature—
explaining change as changes in qualities—no
mathematics.
• A distinctive feature of the new science was the
formulation of mathematical laws and the
replacement of qualitative descriptions with
quantitative ones (time, weight, distance…).
• E.g. v = d/t
• Platonic revival—the relationship between
mathematics and nature.
• As Aristotelian science became more
problematic, scholars in the middle ages
returned to this Platonic notion.
• E.g. Copernicus on his heliocentric model… “we
find then in this arrangement an admirable
harmony of the world, and a dependable,
harmonious interconnection of the motion and
size of the paths, such as otherwise cannot be
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 had adopted the new science and its
mechanical and mathematical explanations to
explain motion.
• As a result of his work, he faced increasing
criticism by the Aristotelians, who were, not
surprisingly on the side of the Church.
• In 1663 he was imprisoned by the Inquisition for
teaching Copernicus’ theory.
Galileo Galilei
• The Aristotelians said “that as he became a
better mathematician he became a worse
physicist, because he moved away from the
world as it appears in simple observations, and
focused instead on abstract and ideal
mathematical descriptions of times and
motions.”
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Challenging Aristotelian Science
(Again)
Challenging Aristotelian Science
(Again)
• This shift in thinking also did damage to
Aristotelian confidence in the reliability of
perception.
• Mathematical laws are idealizations of
what we actually observe.
• The acceptance of mathematical laws did
not follow from their observability, but from
the fact that they produced better
predictions.
• This led the new scientists to think that the real
qualities of objects are not necessarily the ones
we perceive.
• Thus, appearances (observation) may not be the
ultimate guide to understanding the world—even
though it is the appearances we want explained.
• And this ushered in new challenges to Aristotle’s
account of the relation between the perceiving
mind and the physical world—that the real
qualities of objects are not like the sensations
we experience.
Galileo Again
Galileo Again
An Argument Against Aristotelian Perception
• Aristotle thought the qualities we perceive are
features of the objects of perception.
• Galileo argues that this is a misattribution of
things we know with our mind to the objects
themselves.
• Imagine being tickled lightly by a hand or a
feather.
• Everyone agrees the tickling belongs to us and
not to the hand. Right?
Galileo Again
• Galileo explained it instead as a result of the
motion of particles of matter.
• For example, he suggests that sensations of
sound are the result of moving air particles
causing a vibration on the eardrum.
• Differences in vibration Æ differences in the
sensation of sound in the mind.
• If we run our hand over a statue, no one thinks
the statue feels a tickle.
• Thus, the tickling is not a property of the hand
(or feather).
• It exists solely in the mind of the person being
tickled.
• The same goes for the other senses.
• Objects produce the sensation in us, but the do
not possess sensation.
Galileo Again
• For this and other reasons, Galileo thought
that the only qualities that really exist in
material objects are the sizes, shapes, and
motions of the particles that cause
sensations.
• Tastes, odours, sounds, are merely
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
• Descartes was obsessed with the idea that
scientific progress required that we have a
means of examining all beliefs—to separate
those notions that are reliable from those that
are not.
• In short, his goal was to find a secure foundation
for all of our knowledge.
• This is Descartes’ Foundationalism.
• Like Galileo, he challenged the idea that
appearances should be the primary source of
information about the world.
• This was to be achieved by the systematic rejection of
any assumptions that could possibly be called into doubt.
• And on the basis of the foundation and reason alone
(logic) we would secure (deduce) all knowledge.
• Descartes was Rationalist.
• How to doubt? Methodological Skepticism.
• There are two main arguments used to call all that we
can into doubt.
Rene Descartes
Rene Descartes
The Cogito
• Given what has been set out in the previous
arguments Descartes/the reader now has
grounds to doubt all his/her knowledge.
• So where is this foundation that Descartes
intended to find?
• All he needs (like Archimedes) is one point that
is “certain and unshakeable” to found his
knowledge upon.
• But, we have already doubted everything…what
could possibly remain?
• The one thing that seems difficult to doubt
is that, there is some doubting going on.
• Cogito ergo sum: “I am thinking, therefore
I exist.”
• This is the foundational piece of
knowledge Descartes was looking for.
(1) The Dreaming Argument.
(2) The Deceiver Argument.
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From the Mind Onward
• What is a thinking thing?
• It doubts, understands, affirms, denies, is
willing, imagines, perceives…but do all of
these attributes really belong to us?
• They are all merely kinds of thinking.
• So, these ruminations support the idea
that the essence of the mind is thinking—it
is a thinking substance.
From the Mind Onward
•
•
•
•
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What can we know about the external world?
Consider a piece of beeswax.
Examine its sensible qualities.
Tastes like honey; Smells like flowers; has
distinct colour, shape, size…
Now place it near a fire.
From the Mind Onward
From the Mind Onward
• Once again, let’s examine its sensible
qualities.
• The taste is gone; the smell is gone; the
colour and shape have changed, it’s larger
in size…
• So what is essential to the wax?
• It can’t be these sensible qualities since
they have all disappeared.
• But we still see that the wax continues to
exist without them.
• These are merely accidental features of
the wax.
• What we can say, at the very least, is that
the wax takes up space—that it is
extended in general (it has extension).
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From the Mind Onward
From the Mind Onward
• How do we know this?
• The senses never give us a notion of
general extension because all objects
come with a particular shape, size etc.
• Extension is grasped by the understanding
not through our senses.
• So the essential feature of bodies is that
they are extended…and this we know via
the understanding.
• But Descartes realizes that he still can’t be
certain of these claims.
• Thus, he ushers in (non-deceiving) God as
a means of justifying these ideas.
• This is the antidote to the deceiver
argument.
• I will leave aside the argument for the
existence of God.
From the Mind Onward
From the Mind Onward
• Once we accept that a non-deceiving God exists
(since deception would be contrary to his
nature), then we can prove the certainty of our
knowledge.
• Thus, those ideas that are clear (i.e. vivid) and
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.
• Some of these clear and distinct ideas are
built into us—e.g. mathematical ideas.
• These are innate ideas: a perennial issue
in psychology.
Descartes’ Dualism
Descartes’ Dualism
• So now we have two kinds of substances:
thinking substances and extended
substances.
• The essence of the mind is that it is a
thinking substance and the essence of
material bodies is that they are extended
in space.
• On the basis of this Descartes claims that
the mind is distinct from the body—
mind/body dualism.
1. “The fact that I clearly and distinctly
understand one thing apart from another is
enough to make me certain that the two things
are distinct.”…otherwise God is a deceiver.
2. I have a clear and distinct idea of myself as
existing without a body…the essence of mind
is thought…the essence of body is extension.
3. Therefore, I am not my body (or God is a
deceiver).
Mind and body are distinct! Platonism again.
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Descartes’ Dualism
Descartes Dualism
• Descartes thought that the pineal gland was
where the soul was located.
• The reason for this was that all of the other parts
of the brain are double.
• The pineal gland represented
was a single structure that could
house the soul—a unitary object.
• Gilbert Ryle (1949) referred Descartes view as the
“ghost in the machine.”
• As a result of these commitments we can also describe
Descartes as an interactionist—since the immaterial
mind must be supposed to interact with a material body.
• This led to the Mind/Body problem that has been with us
since (Behaviourism/Cognitive Science).
• Descartes also assumed that we know things best
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
according to its own rules, given by God, while
the body is subject to mechanical laws.
• Descartes conceived of the body as a kind of
mechanical device (machine)—this was
informed by some of the latest technological
and scientific developments of the day.
Descartes and the Body
• The fire (A) displaces
the skin, which pulls a
tiny thread (B), which
opens a pore in the
ventricle (F) allowing
the "animal spirit" to
flow through a hollow
tube, which inflates
the muscle of the leg,
causing the foot to
withdraw.
Vaucanson’s Duck
• The development of various tinker toys
that mimicked animal actions were
inspiring (e.g. Vaucanson’s duck).
• 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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Descartes and the Body
• Though Descartes was skeptical that such
innovations would lead to mimicking human
behaviour (Turing Test), he did think it was
possible in the case of animals.
• Though he though humans and animals were
different, he saw no difference between animals
and machines…the were automatons.
• This mechanical approach to the body would, in
later history, be adopted as an approach to the
mind.
Isaac Newton (1642-1727)
More on Descartes
• Descartes had detailed theories about the
nature of perception.
• He developed the first comprehensive account
of the role of emotion in mental life (The
Passions of the Soul).
• He worked to develop a theory of mind/body
interaction—which he later integrated with his
account of the passions.
• Developed a robust methodology for inquiry.
• He had an elaborate cosmology.
Isaac Newton
• Has been described as the ‘greatest scientific
genius the English-speaking peoples have
produced.’
• He studied everything from alchemy to history.
• His most famous work is his Principia—in which
he lays the foundation for classical physics.
• Interestingly, he spends a great deal of time
attacking the cosmology of Descartes, which
was the going theory.
Isaac Newton
Isaac Newton
• One of Newton’s greatest discoveries were his
basic laws of motion.
• E.g. The law of inertia (Law 1).
• These were expressed in mathematical terms
(recall Pythyagoras).
• The fact that all motion (from the planets to small
objects) can be captured by these basic laws was
extremely profound—physics unified science.
• It suggested that the world was governed by
these basic immutable (mathematical) laws.
• Science is an attempt to provide general
explanations of this sort.
• Psychology as a science strives to discover the
laws of human behaviour, thought, perception,
etc.—psychological laws.
• Further, many psychologists have attempted to
emulate the physical sciences by treating
psychological events as physical events that
follow the same laws that regulate other physical
systems.
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Isaac Newton
Isaac Newton
• In this way, psychology as a subject matter is treated
essentially the same as physics—both study the motion
of physical systems (motion of objects vs. motion of
organisms—behaviour).
• Just as force is required to move physical objects (given
the law of inertia), it is also required to move organisms.
• And not just any force is sufficient (follows from second
law of motion), it must be a strong enough force to
initiate motion (e.g. pushing a dump-truck).
• Force must exceed a threshold (neuronal excitation;
awareness; hearing…).
• Newton also did work in optics—which was an attempt to
give a physical understanding of light and colour
phenomena.
• His prism experiment showed that light actually could be
split into different kinds of light—that white light is a
composite of other colours.
• He did not think that light had these properties, but it had
the power (disposition) to create the subjective
experience we have of colours.
• Stimulus vs. subjective experience.
• A physical description will not exhaust our subjective
experience.
• Recall Galileo.
Next Class
• The British Empiricists
• Kant
• Maybe Mill and Wolstonecraft.
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