Week 1: Russell. "Our Knowledge of the External World

The Existence of Matter
The Problem of Perception and the External World
Bertrand Russell
Whoever wishes to become a philosopher must learn not to be
frightened by absurdities.
------Bertrand Russell, Problems of Philosophy
An Old Problem
Skepticism about the External World
• Are things as they seem?
• Are there objects independent of
• Are there other minds?
• And even if there are…
• …how could I ever know any of
these things?
Causes of my experiences?
• External objects?
• Berkeley’s God?
• Updated version of Berkeley’s God: I’m a brain in a vat and a
computer is feeding in experiences?
It was at that precise moment that Stanley realized
that he may very well be a brain in a vat.
Problem: how to avoid skepticism
The Classic Alternatives
Direct (“Naïve”) Realism:
physical objects are directly
(“immediately”) perceived
We don’t need to justify an
inference from sensory
experience to physical reality
because physical objects are
the objects of sensory
Sense Data Theories:
the objects of immediate
experience are sense data—
private, non-physical entities,
• Representationalism (indirect
realism): the immediate objects
of experience represent the
physical objects which cause
• Phenomenalism: physical
objects are reducible to the
occurrence of the immediate
objects of experience
Direct & Indirect Realism fail
Russell argues that neither direct realism nor indirect realism can get
us out of skepticism.
Direct Realism: we do need
justification for beliefs about
physical objects.
• Argument from illusion: cases
of non-veridical perception
• Argument from perspectival
• Argument from the scientific
account of perception: the
intervening medium affects
experience, the finite speed of
• Representationalism: we
can’t know either that there
are objects outside of
experience that cause
experience or that whatever
objects there are ‘out there’
resemble the objects of
immediate experience (i.e.
sense data)
• We can’t observe the alleged
causal connection.
• We can’t observe the alleged
Veil of Perception
What’s the problem with this picture?
What we need to do
• Avoid skepticism: give good reason for our commonsense belief that
there is an “external world”
– Why? Because that’s what philosophers do: “philosophy leaves
everything as it is.”
• Explain the relation between our sense data and physical objects
– Phenomenalism: physical objects are “logical constructions” out
of sense-data—”permanent possibilities of sensation” (Mill)
• Explain the relation between our sense data and us—and other
people’s sense data and them
– Neutral Monism: physical objects and “selves” (minds) are
constructed out of the same (“neutral”) items but in different
What Russell Will Do
• Russell will rehearse the case for skepticism
– Hard and soft data: logical facts and facts about sense data are
all that are certain
• How the question should be put: “independent of ourselves” won’t
do because
– What is the self?
– What is meant by independent?
• An hypothesis to fit commonsense talk
– physical objects as logical constructions
What is “given” in sense
The first thing that appears when we begin to analyze our common
knowledge is that some of it is derivative and some of it is
primitive…the immediate facts perceived by sight or touch or
hearing do not need to be proved by argument…[but] what is
actually given in sense is much less than most people would
naturally suppose and…what at first sight seems to be given is really
• Sense perception is “constructive”: not all is “given”
– We fill in the details: listening to English vs. foreign language,
seeing faces, reading people’s expressions, etc.
– We (unconsciously) make assumptions, e.g. about the
persistence of unperceived objects
• For what is not “given” we need arguments
Hard and Soft Data
I mean by ‘hard’ data those which resist the solvent influence of
critical reflection, and by ‘soft’ data those which, under the
operation of this process, become to our minds more or less
• Russell will attempt to sort out the hard data, which requires no
argument from the soft data
• And to produce arguments in support of the ‘soft’ data of science
and common sense.
• The aim is to avoid fruitless skepticism.
• Hard Data: “the facts of sense (i.e. of our own) sense-data and
laws of logic
• Soft Data: persistence of unsensed objects and other minds.
Stating the Problem
The Problem: Can the existence of anything other than our own
hard data be inferred from the existence of those data?
• In the past the problem has not been stated in a non-questionbegging way
• Wrong way of asking the question: “Can we know of the existence
of any reality which is independent of ourselves?”
• This is a bad formulation because it begs the question of
– What the “self” is
• bundle of psychological states or the “bare subject” which
“has” them
– How “independent” is to be understood
• logically independent or causally independent?
The Self
• Why we cannot appeal to the “self” in posing the question
• Suppose the “self” is understood as the subject of psychological
– The self in this sense is inferred, not immediately experienced
(vide Hume!)
– Experience of the self is not hard data—and we agreed to start
with hard data
• Suppose the “self” is “the whole assemblage of things that would
necessarily cease to exist if our lives came to an end.”
– What are these things? Back to the question of sorting out the
– In what sense are they “dependent” on us s.t. they’d cease to
• Logical independence: it is logically possible for one thing to exist
without the other
– logical possibility: conceivability, doesn’t involve a contradiction
– Russell claims one thing is logically dependent upon another
only when it has the other as a part: e.g. the book is logically
dependent on its pages. Is this true?
– This brings us back to the question of what the Self is.
• Causal independence: “there is no causal relation between the two
such that the one only occurs as the effect of the other.”
• We can’t determine this because we’re stuck behind the Veil
of Perception!
Setting the Question
The Problem: Can the existence of anything other than our own
hard data be inferred from the existence of those data?
• We need to distinguish two separate questions
1. Can we know that objects of sense, or very similar objects,
exist at times when we are not perceiving them?
2. If this cannot be known, can we know that other objects,
inferable from objects of sense but not necessarily resembling
them, exist either when we are perceiving the objects of sense
or at any other time?
• We can’t answer (2) because “both the thing-in-itself of philosophy
and the matter of physics present themselves as causes of sensible
• Russell is offers a response to (1)
Logical Constructions and Inferred Entities
Whenever possible, substitute constructions out of known entities for
inferences to unknown entities.
Objects of a kind, F, are said to be
“logical constructions” out of objects
of another kind, G, if the facts about
Fs reduce to facts about Gs, or
everything said using the F vocabulary
may be said in a more basic or
fundamental way referring only to Gs.
The Average Plumber has 2.3 children.
Logical Constructions and Inferred Entities
• The Average Plumber is a logical construction.
• There is no such being as the Average Plumber over and above
regular plumbers!
• The form of the sentence “the Average Plumber has 2.3 children” is
misleading: “the Average Plumber” does not refer to any individual.
• What we mean is that if we divide the number of plumbers’ children
by the number of plumbers we get 2.3.
The Average Plumber
Logical Constructions and Analysis
“The method of ‘postulating’ what we want has many advantages;
they are the same as the advantages of theft over honest toil. Let us
leave them to others and proceed with our honest toil.” Russell
Introduction to Mathematical Philosophy
• We prefer logical constructions to (“postulated”) inferred entities in
the interests of epistemic security
• We get into trouble with talk about “the average plumber” because
of a mistaken understanding of language: we imagine that wherever
there’s a noun or noun it must be the name of some object.
• We need to distinguish surface grammar from logical form to
paraphrase away the Average Plumber and other weird non-entities
Surface Grammar vs. Logical Form
• Al did the wash for Betty’s sake
• Surface grammar suggests that this sentence is about 4 things: Al,
the wash, Betty…and a sake that somehow Betty has.
• But there are no such things as sakes, as the true logical form of this
sentence shows
• Al did the wash in order to help Betty.
• Doping out the true logical form beneath the “surface grammar” is
taken to be one of the chief projects of analytic philosophy by
Russell: this is “analysis.”
Physical Objects as Logical Constructions
• Russell is going to suggest that we understand physical objects as
logical constructions out of the ‘hard data’ of sense experience.
• E.g. to say that there’s a table in front of me is to say something
about the various experiences I and others have or would have: to
talk about a certain structure of sensory experiences.
• There is no table over and above that structure of experiences if we
understand claims about physical objects correctly
• And so we can avoid skeptical worries about the existence of
objects behind the Veil of Perception!
Sense Data
• When I speak of a ‘sensible object,’ it must be understood that I do
not mean such a thing as a table, which is both visible and tangible,
can be seen by many people at once, and is more or less
permanent. What I mean is just that patch of colour which is
momentarily seen when we look at the table, or just that particular
hardness which is felt when we press it, or just that particular sound
which is heard when we rap it.
• Sense Data
• We need to state the external world problem without assuming an
answer (i.e. “begging the question”) so we have to state it in terms
of the appearances of the table
• The problem is that there are so many and they’re so different!
• Perspectival variation
• Illusion
Perspectival Variation
A table viewed from one place presents a different appearance from
that which it presents from another place. This is the language of
common sense, but this language already assumes that there is a
real table of which we see the appearances…What we ought to say
is that, while we have those muscular and other sensations which
make us say we are walking, our visual sensations change in a
continuous way…What is really known is a correlation of muscular
and other bodily sensations with changes in visual sensations.
• This perspectival variation is supposed to show that the “sensible
objects” we immediately experience are not physical objects
• Different appearances of the table are different in size and shape—
the one physical object can’t have all those different properties
• Why do we privilege certain appearances as the “real” sizes or
shapes of physical objects?
We can shut one eye, or put on blue spectacles…Physiological
changes also alter the appearances of things…Experience has
taught us that where we see certain kinds of coloured surfaces we
can, by touch, obtain certain expected sensations of hardness or
softness, tactile shape, and so on…But the mere fact that we are
able to infer what our tactile sensations would be shows that it is not
logically necessary to assume tactile qualities before they are felt.
• Arguments from illusion too are supposed to show that the “sensible
objects” we immediately experience are not physical objects
• Things don’t always appear to be as the “really are.
• Things that really aren’t appear to us in dreams, hallucinations,
mirages, etc.
• Why do we privilege some appearances as veridical while
dismissing illusions, dreams, etc. as non-veridical?
On Not Begging the Question
• We cannot speak legitimately of changes in the point of view and the
intervening medium until we have already constructed some world
more stable than that of momentary appearances.
• We cannot appeal to science—e.g. to optics and the science of
perspective, to neurophysiology or physics—because science
assumes that there is a world more stable than that of momentary
• Philosophy is not…
– an alternative “worldview” to the scientific or commonsensical
– a body of doctrines that conflict with science or commonsense
The External World Problem
Can the existence of anything other than our own hard data be
inferred from these data?
• The hard data of sense experience are sense data, which cannot be
identified with ordinary physical objects given perspectival variation
and the possibility of illusion.
• We can’t assume that our experiences are caused by concurrently
existing objects outside of experience.
• We can’t appeal to the testimony of others because this assumes
the existence of objects outside of our experience, viz. other minds.
• We can’t appeal to science or commonsense because we are
looking for explanation and justification of scientific and
commonsensical claims!
Russell’s Provisional Solution
Instead of inquiring what is the minimum of assumption by which we
can explain the world of sense, we will, in order to have a model
hypothesis as a help for the imagination, construct one possible (not
necessary) explanation of the facts.
• The system of “perspectives”: all views of the universe, perceived
and unperceived, including the private spaces of actual perceivers.
– There are as many private spaces as there are
perspectives…but there is only one perspective-space, whose
elements are single perspectives, each with its own private
• Our problem is that of constructing our common world—including
physical space and its occupants—from these private perspectives,
whose occupants constitute the hard data of experience.
The Penny Example
• Private spaces are ordered by means of their
similarities…we start from one which contains
the appearance of a circular disk…then form
a whole series of perspectives containing a
graduated series of circular aspects of varying
• We can form another straight line of
perspectives in which the penny is seen endon and looks like a straight line of a certain
A Way the World Could be
• We may define ‘here’ as the place, in perspective space, which is
occupied by our private world…A thing is near to ‘here’ if the place
where it is near to is my private world.
• [T]wo places in perspective space are associated with every aspect
of a thing…Every aspect of a thing is a member of two different
classes of aspects, namely: (1) the various aspects of the thing, of
which at most one appears in any given perspective; (2) the
perspective of which the given aspect is a member.
• The physicist naturally classifies aspects in the first way, the
psychologist in the second.
• The world we have constructed can, with a certain amount of
trouble, be used to interpret the crude acts of sense, the facts of
physics, and the facts of physiology. It is therefore a world which
may be actual. It fits the facts, and there is no empirical evidence
against it; it also is free from logical impossibilities.
What is real?
• Russell’s view may be interpreted as a version of Neutral Monism
according to which what there is in the world is neither intrinsically
mental nor physical—hence “neutral.
• The same things belong to two different classes: one way of
classifying them is of interest to physicists; the other way to
• ‘Real things’ are aggregates of the world’s constituents that hang
together in a coherent way—a way of classifying them that’s useful
for explanation and prediction. For example…
• The hypothesis that other people have minds…is a hypothesis
which systematizes a vast body of facts and never leads to any
consequences which there is reason to think false. There is
therefore…good reason to use it as a working hypothesis.
Against Skepticism
Our hypothesis…shows that the account of the world given by
common sense and physical science can be interpreted in a way
which is logically unobjectionable, and finds a place for all the data,
both hard and soft. It is this hypothetical construction, with its
reconciliation of psychology and physics, which is the chief outcome
of our discussion.
• By understanding sense-data, the objects of direct acquaintance, as
the fundamental constituents of the world we take as our starting
place the ‘hard’ data of experience, which is self-evident and
requires no argument.
• By eliminating “inferred entities” in favor of “logical constructions”
we avoid skepticism
• And provide an account of the world that is consistent with science
and common sense.
The Elephant is Constructed
The End