The Problems of Philosophy

Philosophy 1

Spring, 2002

G. J. Mattey

Bertrand Russell

• Born 1872• From England• Aristocrat• Anti-war activist• Won Nobel Prize for

literature (1950)• Author of popular

essays• Died 1970

Russell’s Contributions

• Discovered, and tried to solve, “Russell’s paradox” in the theory of sets

• Published first widely-read treatise on symbolic logic (with A. N. Whitehead)

• Tried to reduce mathematics to logic (logicism)• Applied symbolic logic to philosophical problems• Co-founder of analytic philosophy (with G. E.

Moore)

Perceptual Relativity

• We think that our ordinary beliefs are certain, e.g., I am sitting at a table of a specific shape

• But these beliefs are very likely to be wrong• We describe the table on the basis of what we see

and feel, and we think others would describe it in the same way

• But the description only reflects our own point of view

• No two people see and feel it the same way

Appearance and Reality

• A painter is concerned with appearance, a practical person with reality

• The philosopher wants to know what appearance and reality are

• Perceptual relativity shows that color is merely appearance: the table has no single color

• The same considerations hold for shape, hardness• The real table is not immediately known by sense

Two Questions

• Is there a real table at all?

• If there is a real table, what are its real characteristics?

• Both are very difficult to answer

Sense-data

• Sense-data are things immediately known in sensation

• Sensation is the experience of being immediately aware of sense data

• Colors, shapes, textures are sense-data• So, a sensation of color is the sensation of a sense-

datum• The sense-data are not the table or properties of

the table, so how are they related to the table?

Idealism

• Objects such as tables are physical objects• The collection of physical objects is matter• Berkeley tried to show that matter does not

exist at all, and at least succeeded in showing that its existence is not certain

• He admits that sense-data are signs of something mental outside us

• The real table is an idea in the mind of God

Existential Doubt

• If we cannot be sure that matter exists, we cannot be sure that other people exist

• We may be all that exists (solipsism)

• Even the “I” might be doubted

• All that is certain is that a sense-datum is being perceived at a time

• This is the solid basis for knowledge

From Sense-Data to Matter

• Do sense-data provide good evidence that physical objects exist?

• Common sense, on the basis of practice, answers in the affirmative

• There must be matter for there to be public objects that are neutral with respect to point of view

• Why believe there are such objects?

Similarity

• One argument for public objects is that there is similarity in people’s sense-data

• But this begs the question, because it supposes that there are other people receiving sense-data

• They may be part of my dreams• So evidence for public objects must come

from our own private experiences

Simplicity

• There is no contradiction in supposing that my private experiences have no public counterpart

• My dreams present elaborate scenes• But it is simpler to explain my sense-data through

public objects• The simplicity is due to the continued existence of

public objects, which accounts for gaps in sense-data

• It also accounts for behavior such as that of a cat’s exhibiting hunger

Human Behavior

• The real advantage of public objects is in the explanation of human behavior

• Sounds and motions are produced that are most simply explained by reference to a body similar to my own

• Public objects can also account for dreams• “Every principle of simplicity urges us to

adopt the natural view”

Belief in Physical Objects

• Our original belief in physical objects is instinctive, not demonstrative

• It seems that the sense-datum is the independent object (Hume)

• There is no good reason to reject the natural belief, given its explanatory simplicity

• It is the task of philosophy to show how our deepest instinctive beliefs form a system

• The possibility of error is diminished by the harmony of the parts of the system

The Nature of Physical Objects

• Science has drifted into reducing the phenomena of nature to motion

• The motions of physical objects are not identical to sense-data (e.g., the light itself)

• Nor is the space we see and feel the space in which physical objects exist– The space we feel and the space we touch are distinct

(Berkeley)

• Private shapes differ when public shapes are static

Correspondence

• Physical objects cause sensation through interaction with a physical body

• Changes in sense-data should reflect changes in bodily position relative to objects

• The senses testify in favor of one another• Other people confirm what we belief• So we may assume that there is a physical space

corresponding to our private space

Knowledge of Physical Space

• We can know of physical space only what is required to explain the correspondence

• For example, we can know that the moon, earth, and sun are in a line to explain the appearance of an eclipse

• But our knowledge is limited to relations of distance and does not extend to distances themselves

Knowledge of Time

• The private feeling of duration is a poor guide to public durations

• But the order of public events corresponds to that of private experiences, “so far as we can see” (and this holds for space)

• The correspondence is not exact– Lightning is really simultaneous with thunder– The light we see left the sun eight minutes ago

Knowledge of Physical Objects

• Differences in sense-data correspond to some differences in physical objects

• We have no direct acquaintance with the properties in the physical objects

• We know only the relations they hold to one another

• The intrinsic properties cannot be known through the senses

• It is gratuitous to think that any sense-data resemble properties of physical objects

Idealism

• Idealism is the doctrine that what exists (or is known to exist) is in some sense mental

• This doctrine is absurd from the point of view of common sense

• But we only know of public objects that they correspond to sense-data

• We cannot reject the doctrine that the intrinsic character of public objects is mental simply because it is strange

Berkeley’s Argument for Idealism

• The existence of sense-data depends on us• Sense-data are immediately-known ideas• All we know immediately about common objects

(e.g., a tree) is the sense-data• There is no reason to think that we know anything

else about them• So the being of a tree is its being perceived• Its public character is explained through God

Fallacies

• To know a tree, it must be “in” our minds, but only as thought of

• But it does not follow that it is “in” our minds as a private object– When I have my wife in mind, she does not exist there

solely as a private object

• An idea exists in the mind as an act, but its object may be “before the mind” while it exists outside the mind

Acquaintance

• An argument for idealism is that what we are not acquainted with is of no importance for us, and so does not exist

• It is granted that we do not know in the sense of being acquainted with matter

• But it is of importance to us• And we can know things with which we are not

acquainted—we can know by description through general principles

Knowledge of Things

• The simplest kind of knowledge of things is by acquaintance, as with sense-data

• Knowledge of things by description requires knowledge of truths: general principles

• Acquaintance with does not yield knowledge of truths– I know the color directly but I do not thereby

know any truth about the color

Knowledge by Description

• We know things by description as “the so-and-so”

• The table is “the physical object which causes such-and-such sense-data”

• To know the table, we must know general truths about causality

• Knowledge by description rests on knowledge by acquaintance as a foundation

Objects of Acquaintance

• Our knowledge would be very limited if we were only acquainted with sense-data

• Memory extends sense-data• We also have higher-order acquaintance with our

states of being aware (self-consciousness) • For example, acquaintance with seeing the sun is

with the fact “Self-acquainted-with-sense-datum”• I know that I am acquainted with this sense-datum

Definite Descriptions

• We are also acquainted with universals such as whiteness, diversity, brotherhood

• This is required for the use of language• A definite description is of the form “the so-and-

so”• When we know an object by description, we know

it as “the so-and-so”• Definite descriptions imply existence and

uniqueness

Knowledge by Description

• Descriptions can be nearer or further from the things with which we are acquainted

• We know the things described only through the components of a description with which we are acquainted

• But we can use descriptions to go beyond the limits of private experience, as in the case of physical objects