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 “pre-critical” 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

ancestry• University Professor at

Königsberg• Banned from writing

on religion• Died 1804

Kant’s Contributions

• Wrote extensively on the physical and human sciences

• 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

sciences

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 itself

• Mathematics became a science when it was seen that we know the properties of figures through construction

• 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

• 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 freedom

• 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 scholars

• 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

Critique

• Reason seeks to establish its own limits• Critique can cut off the roots of dangerous thinking

– Materialism– Fatalism– Atheism– Lack of faith– Fanaticism– Superstition– Idealism– Skepticism

Composite Cognition

• Cognition begins with experience• But it does not therefore arise from

experience• Cognition has two components• An a priori contribution of our cognitive

power (form)• An a posteriori contribution from the senses

(matter)

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 experience

• 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 cause

• 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

subject)– 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 line

• Mathematical judgments are a priori (strictly universal and necessary)

• Then how is pure mathematics possible?

Pure Natural Science

• General principles of natural science are synthetic

• 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?

Metaphysics

• 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 priori

• A system of pure reason would present synthetic a priori cognitions as a system

Intuition

• Cognition relates to objects directly through intuition

• 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

Appearance

• Sensation is the effect of an object on the receptive faculty

• 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

• 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

• Geometry yields synthetic a priori judgments– The predicate amplifies the subject– They are made independently of perception of their

objects– 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

Ideality

• 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

view• So, things in space exist only from the

human point of view• Space and things in it are ideal

Reality

• 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

• 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 objects– 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

succession

• 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

Illusion?

• Does the fact that outer objects and my inner state are transcendentally ideal mean that they are illusory?

• 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 illusion• 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 existence

• 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 understanding

• Both may be empirical or pure– Empirical cognition has sensory elements– Pure cognition is free of sensory elements

• Cognition arises only from their union

Logic

• General logic concerns rules of thought that apply to all objects that can be thought– Pure general logic concerns formal rules of

thought– 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 empirical

• 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

• 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

Completeness

• 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

Functions

• 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

Synthesis

• The mind is initially given a manifold of presentations– 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

synthesis• 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,

community)– 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 objects

• 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