Rene Descartes
and
CARTESIAN EPISTEMOLOGY
scepticism: Our knowledge of reality begins with doubt (in modern philosophy
the famous Cartesian doubt). I must first doubt all that I can possibly doubt. I
can doubt the existence of God, other selves, and the existence of the material
world including my own body. Descartes goes so far as to postulate the
existence of the “evil genius,” who might even be able to deceive me concerning
the clear and distinct ideas I have in mathematics.
subjectivism: I find that I can plausibly doubt the existence of everything
except the existence of my own consciousness (the famous “Cogito ergo sum” or
“I think therefore I am”).
rationalism: I will accept as true only what my own reason leads me to
conclude is true through my clear and distinct ideas. Even the “evil genius” is
not able to deceive me concerning the existence of my own consciousness. Now
because of the many imperfections I perceive within my own consciousness, I
know that the idea of perfection could not possibly come from myself. Since
perfection necessarily involves existence (the ontological argument), there must
be a perfect Being or God. God, being perfect, could not possibly deceive me. I
can now trust all of my clear and distinct ideas.
dualism: Through his clear and distinct ideas, Descartes came to accept his own
existence, the existence of God, of other selves, and of the world separate from
my own consciousness, God’s consciousness, and the consciousness of other
selves. Reality is thereby divided between consciousness (res cogitans, thinking
stuff or reason) and everything else (res extensa, extended stuff or what is
visible and measurable).
EPISTEMOLOGY
JOHN LOCKE (1632-1704)
Empiricism
Locke argues that the simplest way to account for all our
knowledge is to assume that our mind is at first a tabula rasa
or blank slate. To introduce innate ideas is superfluous and
we should accept the simplest explanation (Ockham’s Razor).
Since our mind is at first a blank slate, it follows that all our knowledge arises
from sensation.
Simple Ideas
First, we apprehend through sensation simple ideas like “solidity,” “yellow,” and
“motion.”
Complex Ideas
Second, we form complex ideas, which are (1) compounds of simple ideas (e.g.,
“Beauty,” “gratitude,” “a man,” “an army,” “the universe”), (2) ideas of relations
(“larger than,” “ smaller than”) created by setting ideas next to each other and
comparing or contrasting them, or (3) abstractions, wherein the mind separates
out a feature of an idea and generalizes it (e.g., “blueness”).
Primary Qualities
Characteristics that necessarily inhered in material bodies, such as solidity,
extension, figure, motion or rest, and number.
Secondary Qualities
Qualities which are nothing in the objects themselves but powers to produce
various sensations in us by the primary qualities which are in the objects. Such
secondary qualities are colors, sounds, tastes, odors, and tactile sensations.
Degrees of Knowledge
Locke distinguishes: (1) intuition, whereby the mind immediately apprehends a
truth, e.g., when we know that white is not black and that three are more than
two, and when I know that I myself exist; (2) demonstration, where intervening
ideas are needed to perceive the agreement or disagreement of ideas, e.g.,
when we come to know that the three angles of a triangle are equal to two right
angles and that God exists since I myself require some reality which exists in
itself from eternity in order to account for my own existence ( by implication the
argument agrees with the Aristotelian-Thomistic arguments to the “Uncaused
Cause,” the “Unmoved Mover,” and the “Necessary Being”); (3) sensation,
whereby we know the existence of things external to ourselves by their direct
effect upon us through sensation (most directly I apprehend the material
substance which is this desk as the necessary foundation for the primary and
secondary qualities I perceive, and through reflection on the simple ideas of
thinking and willing I can know the spiritual substance of the person next to me).
EPISTEMOLOGY
GEORGE BERKELEY (1685-1753)
Empiricism
Berkeley accepts Locke’s simple explanation that all our
knowledge comes from sensation. However, Berkeley concludes that primary
qualities are no more than interpretations of relations between secondary
qualities (e.g., when I speak of “size” and “shape” by contrasting the “brown” of
the “desk” against the “white” of the “wall”). There is no reason to assume the
existence of any material substance. However, I do know that spiritual
substance exists, since I can infer the existence of the notions of self, God, and
other selves from observing the ideas which come through sensation. My own
existence is immediately inferred from my ideas and sensations, upon reflection
other selves are inferred, and God is inferred as the necessary First Cause, First
Mover, and Being responsible for the ideas and sensations which can not possibly
arise from my finite or other finite selves. It follows that God is necessary to
account for all finite spiritual substances as well. For Berkeley, esse is percipi or
to be is to be perceived. God explains the stability and order of all sensations
and ideas, as well as the existence of other spiritual substances.
EPISTEMOLOGY
IMMANUEL KANT
(1724-1804)
Kant agrees with the empiricists that all our knowledge begins with experience. On
the other hand, he agrees with the rationalists that reason supplies the form of our
knowledge (the way we relate our ideas and draw our conclusions). Kant divides the
mind into three faculties: intuition or perception; understanding; and reason. He
then performs what he calls a transcendental analysis of each faculty: accepting as
simple fact that we do intuit or perceive, understand, and reason, Kant asks “What are
the transcendental conditions that make this possible?” He concludes that there are
transcendental forms or categories of the mind which enable the faculties to
apprehend phenomena or objects of experience. The drawback is that for Kant we
can never apprehend noumenal reality or “the thing-in-itself.”
Faculty of Intuition or Perception
Here we arrive by transcendental deduction at the categories of space and time as
the necessary a priori conditions which make our synthetic propositions concerning
phenomena or objects of experience possible. Everything we experience must be
experienced in space and time. Note that space and time are themselves not objects
of experience.
Faculty of Understanding
Here we discover the synthetic a priori foundations necessary to explain the relations
we perceive. These transcendental categories are unity, totality, causality, and
substantiality. Like space and time, none of these are objects of experience
themselves.
Faculty of Reason
Here our mind produces what Kant calls “pure concepts” and does not discover any a
priori conditions for further synthetic propositions. In other words, the pure
concepts of reason do not relate to any possible objects of experience or
phenomena. The pure concepts of reason are God, soul, freedom, justice, and
immortality. These become the necessary conditions for our practical reason or
moral judgment. The simple fact that we do make moral judgments indicates the
need for freedom, justice, and soul. Furthermore, Kant argues that morality
demands as the summum bonum or highest good that our will and feelings come
into perfect harmony with what morality or moral law demands. He argues that we
need immortality to accomplish this and attain happiness, which requires a harmony
of will and Nature, which only God can bring about.
Epistemology - the branch of philosophy that studies the nature,
sources, limitations and validity of knowledge.
Rationalism
Rationalism - the position that reason alone, without the aid of
sensory information, is capable of arriving at
some knowledge, at some undeniable
truths.
Basic knowledge = arrived at by perception.
Perception is the process of
seeing, hearing, smelling,
touching and tasting by which
we become aware of ordinary objects.
 Rationalists believe that we can acquire accurate knowledge about
the world simply by looking into our minds.
 Knowledge = a priori - pertaining to knowledge that is logically
prior to experience; reasoning based on such knowledge.
The dilemma:
How can we know anything about the world without first observing
it?
What about the mathematician?
Many laws of nature have been established outside of sensory
observation?
math
(analytic geometry, algebra, calculus, trigonometry)
physics
logic
Remember: rationalists do not necessarily believe that knowledge is
arrived at through reason alone. Knowledge can also be arrived at
by sensory observation ie. a giraffe has spots.
And then we have Descartes:
René Descartes - an extreme rationalist. He believes that the mind
is entirely separate from the body. This idea is known as Cartesian
dualism.
 Descartes claims that the senses cannot be trusted.
 Our sense perceptions may = dreams/hallucinations. Therefore
the senses distort our view of reality = unreliable knowledge
source.
 Descartes soon came to doubt everything that he could not prove
to be certain.
 The one certainty = that he exists.
 Confirmation of existence: I think therefore I am.
 He believes that all knowledge is acquired by the mind and not by
the senses.
Empiricism
empiricism - the position that knowledge has its origins and derives
all of its content from experience.
A reaction to rationalism
To empiricists, knowledge is a posteriori = pertains to knowledge
stated in empirically verifiable statements; inductive reasoning.
John Locke - claims the mind is a blank slate on which experience
makes its mark.
All knowledge has its origins in sense experience
The dilemma:
Can we trust our senses?
 Locke claims that our knowledge of things is really our knowledge
of our ideas of things.
 Qualities of an object distinct from our perception =
primary qualities
primary qualities can be measured objectively.
These qualities would exist whether we perceived
them or not.
OBJECTIVE
 Qualities that we discern from an object through observation =
secondary qualities
secondary qualities = qualities that we impose on
an object: colour, smell, texture, etc.
SUBJECTIVE
George Berkeley - agrees with Locke re. ideas originate with
sensory experience. However, Berkeley thinks that primary
qualities could also be subjective.
For Berkeley, only minds and ideas exist.
a subjectivist - no entity can exist without a
perceiver.
Berkeley (interpreted to the extreme) = solipsism - an extreme
form of subjective idealism, contending that only I exist and that
everything else is a product of my subjective consciousness.
The dilemma:
Do objects cease to exist when I am not observing them?
 To deal with this problem, Berkeley claims that things
continue to exist even when no human mind is perceiving
them, because God is forever perceiving them.
 Therefore objects do continue to exist outside our individual
perception.
Berkeley sees people as a collection of ideas. The ideas = based on
subjective experience. Therefore, nothing exists independently of
the consciousness of the observer.
Can we really know if an object exists?
David Hume - pushes Locke's view to the limit.
Hume = a skeptic
skepticism - in epistemology, the view that varies between doubting
all assumptions until proved and claiming that no knowledge is
possible.
For Hume - perception = senses + experience
perceptions take two forms - impressions and ideas
impressions - the initial experience of an object or event
ideas = memory of an object or event
 Prior sense impressions help us make sense of our world.
 If there are no impressions, there are no ideas.
The dilemma:
What about external reality?
Hume claims that external reality is an illusion because there is no
way to verify its existence.
With no external reality there is:
no self
no God
Hume holds that ideas should never be trusted unless they can be
corroborated with some kind of independent sense experience.
Transcendental Idealism
transcendental idealism - in epistemology, the view that
 the form of our knowledge or reality derives from reason
 but its content comes from our senses.
Immanuel Kant - wants to deal with the skepticism of David Hume.
 Kant rejects the rationalist claim to a priori knowledge.
 Kant also rejects the empiricist claim that all knowledge comes
from sense perception.
Kantian epistemology:
Knowledge
Content - comes from sensory experience
Form - comes from reason
 Knowledge is acquired by our innate search for causal
explanations for events.
 Because we are constantly looking for the causes of events, our
mind is an instrument that imposes structure on the world that we
live in.
 The world around us is a world that our mind constructs - the
world must conform to our minds.
The dilemma:
What about a mind-constructed world that do not conform to causal
laws? ie. dreams.
According to Kant, events must be verified by causal effects.
Scientific Method
Inductive Reasoning - the process of
reasoning to probable explanations or
judgements.
 Francis Bacon: investigate nature through
observation and experimentation.
 John Stuart Mill: use methods of induction find generalizations to support observations.
 Features of the scientific method:
1. accumulate observations
2. infer laws / form generalizations
3. confirm findings
 Inductionists tend to follow the criterion of simplicity = the belief
that the world follows simpler rather than complex laws.
The Hypothetical Method = beyond generalizations.
William Whewell claims that scientific advancements are made by
creative guessing - hypothesis = in general, an assumption,
statement, or theory of explanation, the truth of which is under
investigation.
 scientific inquiry is designed to prove or verify the hypothesis.
 Karl Popper contends that scientific hypotheses must be capable
of being falsified through empirical observation.
Falsifiability - the process of repeatedly attempting
to prove an hypothesis false.
If the hypothesis survives - it = CORRECT.
Paradigm - a scientific research tradition or
scientific model.
Revolution - when an old paradigm is replaced
by a new paradigm.
Notes on the scientific method:
1. It incorporates elements of empiricism, rationalism and
transcendental idealism.
2. Relies on inductive reasoning, generalization and repeated
confirmation of new observations.
3. Uses hypotheses, verified through observation, to guide research.
4. It must be falsifiable: the theory must make predictions that, if it
is wrong, can be shown to be false by observation.
5. Theories must be widely accepted by the community of scientists.
6. Scientific theories must meet five criteria:
 accuracy
 consistency
 reliability
 interconnectedness
 inspiring