Critique of Pure Reason

Critique of Pure Reason
Philosophy 1
Spring, 2002
G. J. Mattey
Gottfried Willhelm Leibniz
Born 1646
From Germany
Invented calculus
Had controversies
with Newton
• Ridiculed by Voltaire
• Died 1716
The Leibniz-Wolff Philosophy
• Leibniz’s views were modified by the German
philosopher Christian Wolff
• Kant worked within this framework in his “precritical” years
• There are two principles governing metaphysics
– Non-contradiction establishes what is possible
– Sufficient reason establishes what exists
• Both operate on the basis of pure reason
Immanuel Kant
• Born 1724
• Prussian, of Scottish
• University Professor at
• Banned from writing
on religion
• Died 1804
Kant’s Contributions
• Wrote extensively on the physical and human
• Proposed the currently-accepted explanation of the
origin of the solar system (“nebular hypothesis”)
• Founder of modern geography
• Tried to reconcile rationalism and skepticism
• Proposed an ethical theory based on pure reason
• Proposed a formalistic aesthetic theory
The Secure Path of Science
• Many scientific endeavors are mere groping
• Logic has traveled on a secure path
• Its sole subject is the formal rules of all
thought, no matter what it is about
• As such, it is only preparatory for all the
other sciences
• Mathematics and physics are other secure
A Priori Cognition
• Thinking of objects, directly or through concepts,
is called “cognition”
• “Cognitions” are intuitions of objects or concepts
of objects
• Theoretical cognition concerns the relation of
objects and concepts
• Practical cognition concerns making the object
actually exist
• Theoretical cognition a priori relates objects and
concepts through the use of thought alone
Revolution in Mathematics
• Mathematics became a secure science through a
revolution in thought
• Mathematicians were merely groping when they
tried to find the properties of figures in the figure
• Mathematics became a science when it was seen
that we know the properties of figures through
• We “think the properties into” figures a priori
Revolution in Natural Science
• Natural scientists were merely groping
when they tried to discover the properties of
objects through mere observation
• Galileo and others showed that we must
investigate nature by experiment
• This requires that reason actively brings its
conceptions to nature and tests them out
• Metaphysics is cognition of objects through
concepts alone
• For example, we seek to establish the existence of
God from the concept of a most real being
• It is not yet on the secure path of science
• Instead, it has engendered endless dispute
• Should we continue the search or give up our
confidence in reason?
Revolution in Metaphysics
• Metaphysics has produced concepts in the hope
that they will conform to objects
• We can reverse the field and hypothesize that
objects conform to concepts
• This reversal is like that of Copernicus
• Concepts that are generated a priori can then apply
to objects necessarily
• “All we cognize a priori about things is what we
ourselves put into them”
Limitations of Metaphysics
• If the revolution in metaphysics is successful, it
will limit the field of metaphysics
• The results of metaphysics will only apply to those
objects that must conform to our concepts
• These objects will be called appearances
• The actual thing in itself is not cognized
• This leaves an opening to fulfill our practical
concerns about what we ought to do
An Example:
Freedom and Necessity
• Metaphysics establishes that appearances are
mechanically determined
• If appearances are things in themselves, then
freedom would be impossible
• But if they are not, there is a possibility of
• I cannot cognize freedom, but I can think it
• Freedom is required for morality, so the limitation
of metaphysics is required for morality
Metaphysics and
Public Interest
• What is lost to metaphysics is of interest only to
• Philosophical “proofs” of God’s existence, of
freedom and of immortality do not influence
ordinary people
• We believe in these things for other reasons
– God: the order, beauty, etc., of the universe
– Freedom: the opposition of duty and inclination
– Immortality: dissatisfaction with a limited life
• Reason seeks to establish its own limits
• Critique can cut off the roots of dangerous
Lack of faith
Composite Cognition
• Cognition begins with experience
• But it does not therefore arise from
• Cognition has two components
• An a priori contribution of our cognitive
power (form)
• An a posteriori contribution from the senses
A Priori Judgments
• An a priori judgment has two characteristics
– Strict universality (no exceptions at all)
– Necessity (we cannot think it without recognizing that
it must be true)
• Mathematical judgments are a priori
• The common judgment that all change has a cause
is a priori
• So Hume’s account of causal reasoning in terms of
custom is incorrect
A Priori Concepts
• Suppose you omit from an experiential
concept everything that is derived from
• Space remains from the concept of body
• Substance remains from the concept of an
object in general
• What is left over after all omission is
derived from the cognitive power
Analytic Judgments
• Analytic judgments are the result of the
clarification of our concepts
• What is thought in the predicate of the
judgment is already thought in the subject
• Example: all bodies are extended
• Analytic judgments are all a priori
Synthetic Judgments
• Synthetic judgments add something in the
predicate not already thought in the subject
• They are expansive
• Example: all bodies are heavy
• The concept of a body does not contain that
of heaviness in it
• The connection is found in experience
A Priori Synthetic Judgments
• Can a subject and predicate be connected
synthetically without appeal to experience?
• Example: everything that happens has a
• Having a cause is not analytically contained
in the concept of something that happens
• What is the unknown X that connects them?
Summary Classification
• Presentation
– Sensation (presents only the modification of the
– Cognition (presents an object)
• Intuition (presents a single directly object)
• Concept (presents objects indirectly, through
characteristics that may be common to many)
• Judgment (connects concepts to other
concepts or to intuitions)
Pure Mathematics
• Mathematical judgments are synthetic
• One does not think the number 12 in thinking the
sum of 7 and 5
• One does not think of the shortest distance
between two points when thinking of a straight
• Mathematical judgments are a priori (strictly
universal and necessary)
• Then how is pure mathematics possible?
Pure Natural Science
• General principles of natural science are
• Example: the quantity of motion in the
world is constant
• But they are also strictly universal and
necessary, and hence a priori
• How is pure natural science possible?
• Some metaphysical judgments are synthetic
• Example: the world must have a first beginning
• These judgments are also necessary and universal,
if they are true
• They have been accepted dogmatically because
they were thought to be analytic
• But if they are supposed to apply beyond
experience, they cannot be justified
Transcendental Philosophy
• What is presented here is only a critique of
the use of reason a priori
• The critique is transcendental
• It deals with our way of cognizing objects a
• A system of pure reason would present
synthetic a priori cognitions as a system
• Cognition relates to objects directly through
• Intuition takes place when and only when
an object is given
• For human beings, objects are given
through a receptive faculty, sensibility
• Thoughts of objects through concepts relate
to them only through intuition
• Sensation is the effect of an object on the receptive
• When an intuition refers to an object through
sensation it is empirical
• An object of empirical intuition is appearance
• Appearance has two sides
– A matter, given in sensation
– A form, lying in the mind a priori
Pure Intuition
• The form of intuition is called pure intuition, since
it is contributed by the mind alone
• Pure intuition is separate from what the
understanding thinks through concepts and what
sensation contributes
• Space is the form of intuition of bodies
• Time is the form of all intuition
• Transcendental aesthetic investigates them
Inner and Outer Sense
• Outer sense presents objects alongside one another
in space
• Inner sense presents states of the mind as
successive in time
• What are space and time?
• They might be:
– Actual beings
– Real relations among actual beings
– Merely intuited relations among intuited objects
• Space is not an empirical concept abstracted from
intuitions of bodies
– We need it to think of relations of bodies
• Space is an a priori intuition
– The absence of space cannot be presented
• Space is not a universal concept
– It is a unique thing, which is prior to its parts
– It is an infinite given magnitude, having its parts within
itself, not having infinitely many instances
• Geometry yields synthetic a priori judgments
– The predicate amplifies the subject
– They are made independently of perception of their
– They are strictly universal and necessary
• This can only be explained by space being the
form of the intuition of geometric objects
• As intuition, space unites geometrical concepts
• As residing in the subject, it allows this unification
to take place a priori
• Space is the form of intuition, so it applies
only to objects as appearances
• It does not apply to things in themselves
• Space exists only from the human point of
• So, things in space exist only from the
human point of view
• Space and things in it are ideal
• The ideality of space is transcendental
– Space is only an a priori condition of intuition
• Space is also empirically real
– Space is a form of outer intuition for all humans
– Objects in space are real in human experience
• The ideality of space cannot be compared
with that of sensory qualities
– Sensory qualities are relative to individuals
Time is an form of intuition, just as is space
Unlike space, time has only one dimension
Parts of time presuppose a single, unified time
Time is infinite, in the sense that any time-period
is a limitation of it, so that it is unlimited
• There can be an a priori theory of time
• Time allows the explanation of change in general
and motion in particular
Ideality and Reality
• Like space, time is transcendentally ideal
– Time is the form of inner sense
– It is prior to the placement of objects in time
• Unlike space, time is the a priori condition for all
– If we present an object as in space, our presentation
itself is in time
• Things in themselves are not temporal, but time is
a condition for the reality of all appearances
An Objection
• When I present objects as in time, my mind
changes its state
• Changes in state take place in time
• So, my presentation of objects takes place
in time
• So, time is prior to the presentation of
objects in time
• So, time is actual
A Reply
• It is conceded that time is actual
– It is the actual form in which objects are presented as in
• But its reality is not transcendental
• It is not an object that exists outside of the act of
presenting objects
• The fact that my presentations follow one another
does not make time something in itself
Space and Time
• Space and time are two sources of cognition
• Appearances are necessarily subject to them
• Because they are forms of cognition, we can
understand how we can make judgments a priori
about them
• If we think of them as existing in themselves, we
have to explain how two non-entities can be the
condition of all objects
• Concepts such as motion or change require
experience and are not a priori
Confused Presentations?
• Leibniz and Wolff held that sensibility is confused
presentation of things in themselves
• Only the intellect yields clear presentations (of
things in themselves)
• But this distinction is purely logical
• The distinction between sensibility and intellect
concerns the nature and origin of our cognitions
• Sensibility provides no presentation at all of things
in themselves
Intellectual Intuition
• Human intuition is sensible and passive
• An intellectual intuition would produce its
own objects (“self-actively”)
• We intuit our own mind by being passively
given successive mental states in time
• So, we do not represent ourselves as an
intellectual intuition would represent us
• Does the fact that outer objects and my inner state
are transcendentally ideal mean that they are
• Illusion results from taking these to be
transcendentally real
• On that assumption, we cannot explain the nature
of space and time
• This is why Berkeley downgraded bodies to
• Even the mind itself would be illusory, since its
states are in time
God’s Intuition
• God cannot be an object of intuition to us or
an object of self-intuition in space and time
• If space and time were conditions for the
existence of all things, they would be a
condition for God’s existence
• Then God could not cognize his own
• God’s intuition must be intellectual
Concept and Intuition
• Intuitions are the result of the passive
reception of sense-impressions
• Concepts are the result of the activity of the
• Both may be empirical or pure
– Empirical cognition has sensory elements
– Pure cognition is free of sensory elements
• Cognition arises only from their union
• General logic concerns rules of thought that
apply to all objects that can be thought
– Pure general logic concerns formal rules of
– Applied general logic concerns the psychology
of reasoning
• Special logic concerns rules (of
methodology) applying to thought about
specific kinds of objects
Transcendental Logic
• Some thoughts about objects are pure, others are
• Pure thoughts have their origin in the
understanding, rather than experience
• A logic of pure thoughts is transcendental
• To be transcendental is to be concerned with the
fact that the origin of a presentation is a priori
• Transcendental logic concerns concepts that arise
in the mind independently of sense-experience yet
are applicable to objects
• Truth is the agreement of a cognition with
the object it is supposed to present
• There is no universal criterion of truth of
material (experiential) cognition of objects
• There is a universal criterion of truth of
formal (a priori) cognition of objects
– The understanding must be in agreement with
its own activities
Analytic and Dialectic
• Analytic is the part of logic that concerns the
formal rules of its use
– Transcendental analytic concerns the rules governing a
priori concepts
– It is a logic of the truth of a priori cognition
• Dialectic is the attempted use of logic to establish
material truths
– Transcendental dialectic concerns the misapplication of
rules governing a priori concepts
– It is a logic of illusion
• Transcendental analytic presents pure
concepts derived from the understanding
• The derivation of these concepts must be
based on a single principle
• This principle should encompass the whole
of the understanding
• So, it should present a complete and
coherent system of pure concepts
• The understanding operates by making
judgments connecting concepts to one
another or to intuitions
• A function is the unity of the act of bringing
many presentations under one concept
• So, judgments are functions of unity of
presentations (concepts or intuitions)
• Concepts are functions of unity of intuitions
Functions of Judgment
• Every judgment combines presentations in
four ways
Quantity (universal, particular, singular)
Quality (affirmative, negative, infinite)
Relation (categorical, hypothetical, disjunctive)
Modality (problematic, assertoric, apodeictic)
Examples of Judgments
• The soul is not mortal (universal, negative,
categorical, assertoric)
• The world exists either through blind chance,
internal necessity or external cause (singular,
affirmative, disjunctive, apodeictic)
• If there is a perfect justice, then the persistently
evil person is punished (universal, affirmative,
hypothetical, apodeictic)
• The component sentences of the hypothetical and
disjunctive forms may themselves be problematic
• The mind is initially given a manifold of
– Space and time are a pure manifold
– Sense-impressions are an empirical manifold
• The imagination synthesizes the manifold
• The understanding brings the synthesis to concepts
• Cognition (presentation of an object) occurs when
a concept is applied to the synthesis
Pure Synthesis
• Sensibility supplies a pure manifold of intuition
(spaces and times)
• This manifold is synthesized by the imagination
• The understanding gives unity to the pure
• The same function that gives unity to the
presentations in a judgment gives unity to pure
synthesis in an intuition
The Categories
• Categories are pure concepts which give unity to
the pure synthesis
• The system of categories parallels the system of
forms of judgment
– Quantity (unity, plurality, allness)
– Quality (reality, negation, limitation)
– Relation (inherence/subsistence, cause/effect,
– Modality (possibility/impossibility, existence,
nonexistence, necessity/contingency)
The Task Ahead
• The table of categories serves to organize a system
of metaphysical principles
• To confirm the legitimacy of the principles, it must
be shown why the categories legitimately apply to
• This is the task of the “transcendental deduction”
• Finally, in the transcendental dialectic, it is shown
how the application of these principles beyond
experience leads to “transcendental illusion”
Some Metaphysical Principles
• All intuitions are extensive magnitudes (in space
and time)
• What is real in an object of sensation has a degree
of intensity (of influence on our senses)
• Substance is permanent in all change
• All changes occur according to the law of
connection of cause and effect
• All perceivable substances in space interact in a
thoroughgoing way with one another