11/27/06
Immanuel Kant
(1724-1804)
The Critique of Pure Reason
(1781, 1787)
(Text, pp. 341-363)
1
Anthem
2
Topics covered in the reading
1 The nature, scope,
& limits of human
knowledge
 a priori & a posteriori
knowledge
 analytic & synthetic
judgments
 synthetic a priori
judgments & how they
are possible
 phenomena, noumena, &
the "transcendental ideas
of pure reason"
2 The transcendental
ideas of pure reason:
self, cosmos, & God
3 Morality & metaphysics:
freedom, immortality, &
God
3
Introductory Note
What is knowledge?
 Answer: Knowledge is verified
("justified") true belief.
 To know is to believe;
 the belief must be true (rather than false);
and
 the belief must be verified ("justified"), i.e.,
proved true.
4
The Rationalist-Empiricist Dispute
According to Kant,
all knowledge begins with sense
experience, but not all knowledge
arises out of sense experience.
5
There are two basic types of
human knowledge:
 a posteriori
knowledge, which
arises from &
depends on sense
experience; and
 a priori knowledge,
which arises from
the operations of
the mind & is
independent of
sense experience
6
The distinguishing characteristics
of pure a priori knowledge:
 Necessity
and
 Strict universality
(no possibility of an
exception)
7
A priori judgments are
necessarily & universally
true (or false),
whereas
a posteriori (empirical)
judgments are never
necessarily or universally true
(or false).*
*They are contingently true (or false).
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A further Kantian distinction
Analytic Judgments
vs.
Synthetic Judgments
9
It's all about subjects
& predicates
10
In an analytic judgment
or proposition,
the predicate makes explicit
(explicates) meanings that are
already implicit in the subject (e.g.,
"a triangle is three-sided").
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In a synthetic judgment or
proposition,
 the predicate adds
to our knowledge of
the subject in a way
that logical analysis,
by itself, cannot
(e.g., "some houses
are white").
 The predicate of a
synthetic proposition
augments & amplifies
our knowledge of the
subject.
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The relationships between
analytic, synthetic, a priori, &
a posteriori judgments
13
Analytic judgments express a priori
knowledge, i.e., they are
necessarily & universally true
(or false),
& they can be verified or falsified
independently of sense experience,
i.e., by logical analysis alone.
(There is no need to test
them a posteriori.)
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"Material objects are
extended in space."
This proposition is both
analytic & a priori.
15
A posteriori judgments
(which must be verified or falsified on
the basis of sense experience,
not through logical analysis)
are always synthetic
(e.g., "material objects have weight").
16
So . . . .
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there are
(uncontroversially)
 analytic a priori judgments,
 synthetic a posteriori judgments, and
 analytic a posteriori judgments (which are
a waste of time, since analytic judgments can be
verified or falsified by logical analysis alone).
In addition to these, Kant claims . . . .
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that there are
synthetic a priori
judgments
(This is controversial!)
19
A synthetic a priori judgment
is one that is
 necessarily & universally true (& thus not
derived from sense experience, i.e., it is
a priori)
 and in which
 the predicate adds something to our
knowledge of the subject that could not be
known merely by logical analysis of the
subject.
20
Examples of synthetic a priori judgments
(according to Kant)
 "Everything that happens has a cause."
 "7 + 5 = 12"
 "A straight line is the shortest distance
between two points [in space]."
 "In all changes of the material world, the
quantity of matter remains unchanged."
 "In all communication of motion, action and
reaction must always be equal."
 "The world must have a beginning."
21
This leads to what Kant calls
"the general problem of pure reason"
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23
To this general question, Kant adds
several subsidiary questions:
 "How is pure mathematical science possible?"
 "How is pure natural science [physics] possible?"
 "How is metaphysics as a natural disposition
possible?"
 "How is metaphysics as a science possible?"
(We will not at this time pursue answers to these questions.)
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Kant's solution of
How are synthetic a priori judgments possible?
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Kant's "Copernican Revolution
in Philosophy"
?
Objects
Mind
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According to Kant,
the mind does not conform to its
objects. On the contrary, the objects
of consciousness conform to the
structure & operations of the mind
itself.
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The structure of the mind
Pure
Reason
(Vernunft)
Understanding
(Verstand)
Categories
Categories
of the Understanding
Sensibility
(Sinnlichkeit)
Forms of
space &
time
Forms of
Sensibility
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Kant's overall view
Transcendental Ideas
& Moral Postulates
(Rational Belief)
Noumena
Reason
(Vernunft)
Understanding
(Verstand)
Categories
Mind
Sensibility
(Sinnlichkeit)
Objects of
Consciousness
Phenomena
Forms of
space &
time
(Knowledge)
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Categories of the Understanding
1 Of Quantity
 Unity (Singularity)
 Plurality (Particularity)
 Totality (Universality)
3 Of Relation
 Substance-Attribute
 Cause-&-Effect
 Community (Interaction)
2 Of Quality
 Affirmation
 Negation
 Limitation
4 Of Modality
 Possibility-Impossibility
 Existence-Nonexistence
 Necessity-Contingency
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The categories of the
understanding
are applicable only to phenomena
that appear to us under the forms of
sensibility (space & time);
they have no legitimate application to
noumena, i.e., realities or alleged realities
that transcend the realm of space & time.
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However,
 in an effort to construct a totally
unified, coherent, & systematic worldview,
 human reason (Vernunft) thinks beyond
the phenomenal realm
 and formulates ideas of realities (i.e.,
possible realities) that transcend the
world of experience.
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This takes us
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from knowledge to
rational belief
The transcendental
metaphysics of Pure Reason
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The Transcendental Ideas
of Pure Reason
Self, Cosmos, & God
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The content of the
transcendental ideas
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The Transcendental Idea of
the Self
 a thinking substance (soul)
 simple & unchangeable
 has a personal identity that persists
through time
 exists in relation to other real things
outside it
 experiencer & thinker
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The Transcendental Idea of
the Cosmos
(or world-in-general)
a unified and infinitely long series of events
the totality of all causal series
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The Transcendental Idea of
God

 The primordial,

single, selfsubsistent, allsufficient, supreme
ground of being
 Supreme creative
& purposive reason
as the cause of the
universe
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The Justification of the
Transcendental Ideas
They are the foundations for reason's
construction & account of the
systematic unity of experience.
40
The Idea of the Self enables
reason to construe
 all of "my" subjective experiences as existing in a
single subject (my "self"),
 all of "my" powers of perception & thought as
derived from a single source (my "self"),
 all changes within "me" as belonging to the states
of one & the same permanent being (my "self"),
and
 all phenomena in space as entirely different from
the activity of thought (i.e., as other than my
"self").
41
In other words, the idea of
the Self
provides me with a metaphysical
foundation for the unity of my
experience.
42
The Idea of the Cosmos
enables reason to
think of the world as if it were a
unified collection or totality of infinitely
long causal series that can be
endlessly investigated by science.
In other words, the idea of the cosmos-as-awhole is a stimulus to scientific inquiry.
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The Idea of God enables
reason to see nature
 as a system
grounded in reason
 and
 pervaded with
purpose
 since God is
Supreme Reason
 aiming at
 the ultimate good of
all things.
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In other words,
 the idea that God (a
supremely rational &
purposive being) is
the cause (creator)
of the universe
 enables us to see
the world as a
teleological
unity
 in which everything
(absolutely everything) serves some
purpose.
45
Kant seems to be saying that,
 unless we assume the existence of the
Self (transcendental ego), the Cosmosas-a-whole, & God,
 the world & our experience of the world
 will lack systematic unity & coherence.
In other words, the world & our experience of
the world cannot be completely intelligible (or
meaningful) without the transcendental ideas of
pure reason.
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However . . . ,
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the transcendental ideas
are "regulative,"
not "constitutive."
That is, they guide or "regulate" our study
of the world by leading us to proceed AS IF
the Self, the Cosmos-as-a-whole, & God are
real.
However, the objects of the transcendental ideas
(Self, Cosmos, & God) do not "constitute" actual
objects of experience; they are "merely" ideal
objects, which, if real, add systematic unity &
coherence to our experience of the phenomenal
world.
48
But we cannot KNOW
whether or not the Self, the
Cosmos, & God are real
because they are "transcendental"
(noumenal) objects, i.e., they are not
phenomena that appear in space & time
& to which the categories of the
understanding can be applied.
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Morality, Happiness, &
Metaphysics
Freedom, Immortality, & God
(The Postulates of Practical Reason)
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Kant's distinction between
 theoretical reason (reasoning about
the universe, the world of nature)
 and
 practical reason (reasoning about
human existence & action)
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As we have seen,
pure reason (i.e., pure theoretical
reason), in seeking to understand the
universe as a whole, formulates certain
"transcendental ideas"
(of Self, Cosmos, & God).
Similarly . . . ,
52
pure practical reason,
 in an effort to see
human existence &
human moral effort
as meaningful,
postulates
the reality of moral
freedom, the
immortality of the
soul, & the existence
of God.
(In the Critique of Practical Reason (1788),
Kant calls freedom, immortality, & God "the
postulates of practical reason.")
53
Freedom of the Will
According to Kant,
morality (the moral law)
tells us what we OUGHT to do.
Thus, morality presupposes
freedom of the will
because, logically speaking,
"ought" implies "can."
54
The existence & nature of the
moral law
 In the Critique of Pure Reason, Kant
assumes the existence of pure a priori
moral laws that determine what we
ought and ought not do.
 In his later works on ethical theory
(see footnote on p. 358 in text), he seeks to
deduce the moral law from the concept
of moral duty (or obligation).
55
According to Kant,
reason discerns a relationship
between morality & happiness.
What is the nature of
that relationship?
56
On this subject,
 there is a difference between the
pragmatic law & the moral law.
The pragmatic law
answers the question,
"What must I do in
order to become
happy?"
The moral law
answers the
question, "What
must I do in
order to deserve
(be worthy of)
happiness?"
57
Moral laws are
 categorical
imperatives,
i.e., absolute &
unconditional moral
commands (e.g., "Be
honest");
 hypothetical
imperatives (e.g.,
"If you wish to have
a good reputation,
be honest").
 they are NOT
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In general, the moral law says,
"Do that through which you
become worthy of happiness."
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Reason is not satisfied
 with morality all by
itself,
 nor with
 happiness all by
itself.
 In a completely good
world, "a system in
which happiness is tied
and proportioned to
morality [which makes
one worthy of
happiness] would be
necessary."
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"What . . . is the supreme
good of the moral world that
a pure but practical reason
commands us to occupy?"
"It is happiness in exact proportion to
the moral worth of the rational beings
who populate that world."
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For such an ideal world to exist, two
things are necessary:
 the existence of God;
 and
 the immortality of
the soul.
 Only God can guarantee
the ideal proportionality of
morality & happiness.
 If happiness &
unhappiness are to be
necessary consequences of
our conduct in the
empirical world, then there
must be a future world in
which the soul lives on.
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That’s all,
folks!
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