Could ask students if it would help to think of vague thoughts…
Perception 2016 revision 3. idealism
Idealism: what I have to teach you
• Berkeley’s idealism: the immediate objects of
perception (i.e. ordinary objects such as tables, chairs,
etc) are mind-dependent objects.
• Berkeley’s attack on the primary/secondary property
• Berkeley’s ‘master’ argument.
• Issues, including:
– it leads to solipsism
– it does not give an adequate account of illusions and
– it cannot secure objective space and time
– whether God can be used to play the role He does.
George Berkeley (1685-1753)
• Second of key triumvirate of C17/C18 British
Empiricists – Locke Berkeley Hume
• Philosopher and also Bishop of Clonmerle
• Key texts:
– ‘A Treatise concerning the Principles of Human
– ‘Three Dialogues between Hylas and Philonous’ (1713)
• ‘Hylas’ – derived from ancient Greek for ‘matter’ – prob.
intended to be Locke
• ‘Philonous’ – ‘mind-lover’ – nous= mind, intellect,
intelligence – Berkeley himself
Idealists, defined by Bertrand Russell
• ‘…they think there can be nothing real--or at any
rate nothing known to be real except minds and
their thoughts and feelings. We might state the
argument by which they support their view in
some such way as this: 'Whatever can be thought
of is an idea in the mind of the person thinking of
it; therefore nothing can be thought of except
ideas in minds; therefore anything else is
inconceivable, and what is inconceivable cannot
exist.‘ (The Problems of Philosophy, chapter 1)
that secondary qualities exist
1. Pleasure and pain are attached to all objects but
cannot be in them.
– All secondary qualities (e.g. heat, bright light) are
accompanied (at base) by pleasure or pain.
– Pleasure or pain can’t be in the objects the qualities
represent, so secondary qualities must be perceiver-
– Philonous: Degrees of heat that aren’t painful and also
ones that are can exist only in a thinking substance!
2. The perceptual variation argument.
Task: in pairs, anticipate or give this argument.
Berkeley’s variations on the perceptual variation
1. Locke’s about placing a hot and cold hand in the same bowl of warm water.
Philonous: Well, now, suppose that one of your hands is hot and the other cold,
and that they are both at once plunged into a bowl of water that has a temperature
between the two. Won’t the water seem cold to one hand and warm to the other?
[To the Direct Realist] the water really is both cold and warm at the same
2. Clouds seen from a distance looking different from ones seen close up: Hylas: I
must admit, Philonous, that those colours aren’t really in the clouds as they seem
to be at this distance. They are only apparent colours…Phil: And I suppose that
real colours are ones that are revealed by looking carefully from close up?
3. Objects seen through a microscope have different colours: Philonous: But a
microscope often reveals colours in an object different from those perceived by
unassisted sight. [And also reveals little animals]
4. Animal perception is different: Philonous: So isn’t it highly probable that
animals whose eyes we see to be differently structured from ours, and whose
bodily fluids are unlike ours, don’t see the same colours as we do in every object?
5. Different colours of light change the apparent qualities of objects: Philonous:
And everyone knows that the same bodies appear differently coloured by candle-
light from what they do in daylight. [Or light from a prism can cause] the whitest
object to appear deep blue or red to the naked eye.
Berkeley’s attack on the PQ/SW distinction
• Berkeley then applies the perceptual variation
argument to primary qualities:
– Hyl:. Colours, sounds, tastes—in a word, all that
are termed ‘secondary qualities’—have no
existence outside the mind…Primary qualities are
extendedness, shape, solidity, gravity, motion, and
rest…and really exist in bodies.
– Phil: But what if the arguments that are brought
against secondary qualities hold against these also?
Berkeley: Primary qualities are really
• Size is perceiver-dependent, as
– the apparent size of objects is relative to body size. Phil: Can a single thing
have different sizes at the same time? Hyl: It would be absurd to think so. Phil:
But from what you have said it follows that the true size of the insect’s foot is
the size you see it having and the size the insect sees it as having, and all the
sizes it is seen as having by animals that are even smaller… your own
principles have led you into an absurdity.
– objects vary in size according to distance. Philonous: But as we move towards
or away from an object, its visible size varies, being at one distance ten or a
hundred times greater than at another. Doesn’t it follow from this too that size
isn’t really inherent in the object?
• Shape is perceiver-dependent
– things look different under the microscope
– ...infer that there is no size or shape in an object from the premise that to one
eye it seems little, smooth, and round, while to the other eye it appears big,
uneven, and angular…You can at any time find out that it does, by looking with
one eye bare and with the other through a microscope.
Berkeley: Primary qualities are really
• Motion is relative to a perceiver (to flies, we are
– Phil.: Isn’t the speed at which a body moves inversely
proportional to the time it takes to go any given distance?
…And isn’t time measured by the succession of ideas in
our minds? …And isn’t it possible that ideas should
succeed one another twice as fast in your mind as they do
in mine, or in the mind of some kind of non-human spirit?
• Solidity is relative to the perceiver:
– Phil.: it is obvious that what seems hard to one animal may
appear soft to another that has greater force and firmness of
limbs; and it is equally obvious that the resistance I feel
when I press against a body is not in the body.
• Berkeley’s conclusion: we can’t therefore say that objects have one
real size, shape, motion, independently of how they’re perceived.
Primary qualities are just as mind-dependent as secondary ones.
– let any one consider those arguments which are thought manifestly to
prove that colours and taste exist only in the mind, and he shall find
they may with equal force be brought to prove the same thing of
extension, figure, and motion. In fact they show it to be impossible that
any sensible quality whatsoever, should exist in an unthinking subject
without the mind. (Treatise, 1710)
• Can you think of a rejoinder to Berkeley’s attack on the PQ/SQ
– Hint: mensuration/measurement, ideal observers
Berkeley’s argument summarised
• Our senses provide us with perceptions or
ideas of physical objects.
• Perceptions or ideas are either of primary or
• But both primary and secondary qualities are
• So the objects of perception are entirely mind-
dependent: physical objects cannot exist
independently of the mind.
An issue with Locke’s view that mind-dependent
objects resemble mind-independent ones
• Remember: Locke asserts that primary qualities resemble our
experiences of them, but that secondary qualities don’t.
• Berkeley asks how something (he says) we can’t experience (i.e. the
shape of a physical object in itself) – be known to resemble
something that we can experience (the various perspectives we
have on the object)?
• He asks: which of the various perspectives is correct?
– How can fleeting and variable sensations be known to resemble a
constant object, when there is no more constancy in our perceptions
of primary qualities than there is of our perceptions of secondary
ones? Take shape. Objects can look both circular and ovoid.
• Locke is saying that one of these resemblances is the true shape of
the object. But how can we tell which is which?
– Which of the many is the true size, shape, motion, solidity?
Another issue with Locke’s view that mind-dependent
objects are caused by mind-independent ones
• This issue is raised by philosophers as disparate as Descartes and Berkeley.
• It hinges on the notion that minds and physical objects are utterly
different in nature.
• And then asks how things so different in nature can meaningfully be said
to causally interact: what is the nature of this causation?
– Thoughts only lead to other thoughts.
– Physical events only to other physical events.
• How can it make sense to suggest that physical events are caused by
mental events, and vice-versa?
• This problem is studied in the philosophy of mind, and does not have an
agreed solution, three centuries later.
• Some philosophers, such as the philosopher of mind David Chalmers, call
this problem ‘The Hard Problem’ of consciousness. Chalmers: ‘It is widely
agreed that experience arises from a physical basis, but we have no good
explanation of why and how it so arises.
• Philonous (Berkeley’s mouthpiece) has another sophisticated
argument which derives from Berkeley’s empiricist account of
– Mind-independent qualities depend on mind-dependent
qualities to be known.
– Berkeley argues that our notions of primary qualities are
derived from secondary ones (not the other way around).
– He then enquires after the empirical evidence that Locke is
drawing on to formulate these abstract ideas of motion,
extendedness (3D presence etc) and suggests that it’s not
sufficient to explain how we have these abstract ideas
– So we can’t really have them…
Another issue with Locke’s view that mind-dependent
objects resemble mind-independent ones
The (empiricist) maxim that every
thing that exists is particular
Phil: What distinguishes one instance of motion, or of extendedness, from
another? Isn’t it something sensible—for instance some speed, or some size
and shape? …[yet] these qualities—namely, absolute motion and absolute
extendedness—which are stripped of all sensible properties, have no features
making them more specific in any way... they are extendedness in general, and
motion in general. ...But everyone accepts the maxim that every thing that
exists is particular. How then can motion in general, or extendedness in
general, exist in any corporeal substance? …If you can form in your thoughts a
distinct abstract idea of motion or extendedness, using none of those sensible
qualities which we agree exist only in the mind, then I’ll capitulate. But… if
you can’t, it will be unreasonable for you to insist any longer on something of
which you have no notion… Can you even separate the ideas of extendedness
and motion from the ideas of all the so-called secondary qualities?
Is Berkeley right to suggest that primary qualities are abstract ones, and
we cannot form them apart from our secondary perceptions of them?
Berkeley’s conceivability or ‘Master’ argument
• the term ‘Master Argument’ was first used by
Berkeley scholar Andre Gallois in 1974.
– Also known as the ‘conceivability’ argument
– ‘Master Argument’ as it’s the most important of
– And Berkeley makes it in several places
• in ‘A Treatise Concerning the Principles of Human
• And in ‘Three Dialogues between Hylas and Philonous’
Berkeley’s ‘Master argument’ in
• the concept of matter includes the idea that it exists
• but to conceptualise is to perceive as both are activities
of the mind.
• so the notion of unperceived concepts is contradictory
• and what is contradictory cannot be real
NB he is not arguing for the unreality of the world, but
for the reality of ideas
The Treatise’s 1710 formulation of the
…they will have our ideas of the primary qualities to be
patterns or images of things which exist without the mind,
in an unthinking substance which they call Matter. By
Matter, therefore, we are to understand an inert, senseless
substance, in which extension, figure, and motion do
actually subsist. But it is evident from what we have
already shown, that extension, figure, and motion are only
ideas existing in the mind, and that an idea can be like
nothing but another idea… Hence, it is plain that that
the very notion of what is called Matter or corporeal
substance, involves a contradiction in it.
Berkeley’s Master Argument continued
That neither our thoughts, nor passions, nor ideas formed by
the imagination, exist without the mind, is what everybody
will allow. And it seems no less evident that the various
sensations or ideas imprinted on the sense, however blended or
combined together (that is, whatever objects they compose),
cannot exist otherwise than in a mind perceiving them…as to
what is said of the absolute existence of unthinking things
without any relation to their being perceived, that seems
perfectly unintelligible. Their esse is percepi, nor is it possible
they should have any existence out of the minds or thinking
things which perceive them.
Write down a couple of key phrases
Berkeley’s ‘Master’ argument, continued
It is indeed an opinion strangely prevailing amongst men, that
houses, mountains, rivers, and in a word all sensible objects,
have an existence, natural or real, distinct from their being
perceived by the understanding. [But does this idea not]
involve a manifest contradiction? For, what are the fore-
mentioned objects but the things we perceive by sense? What
do we perceive besides our own ideas or sensations? and is it
not plainly repugnant that any one of these, or any
combination of them, should exist unperceived?…just as it is
impossible for me to see or feel anything without an actual
sensation of that thing, so is it impossible for me to conceive
in my thoughts any sensible thing or object distinct from the
sensation or perception of it.
From what has been said it follows there is not any other
Substance than Spirit, or that which perceives.
Restate Berkeley’s ‘Master’ argument’
But look into your own thoughts, and so try whether you can
conceive it possible for a sound, or figure, or motion, or colour
to exist without the mind or unperceived. This easy trial may
perhaps make you see that what you contend for is a downright
contradiction. …I insist, to wit, that the absolute existence of
unthinking things are words without a meaning, or which
include a contradiction.
Discuss: can you think of a thing that exists without you
Issues with Berkeley’s master
Russell thinks that Berkeley has tied himself in conceptual knots by not
distinguishing adequately between the object of knowledge and the
act of perception
"If we say that the things known must be in the mind, we are either
un-duly limiting the mind's power of knowing, or we are uttering a
mere tautology. We are uttering a mere tautology if we mean by 'in
the mind' the same as by 'before the mind', i.e. if we mean merely
being apprehended by the mind. But if we mean this, we shall have to
admit that what, in this sense, is in the mind, may nevertheless be not
mental. Thus when we realize the nature of knowledge, Berkeley's
argument is seen to be wrong in substance as well as in form, and his
grounds for supposing that 'idea'-i.e. the objects apprehended-must
be mental, are found to have no validity whatever. Hence his grounds
in favour of the idealism may be dismissed.“ – ‘Problems of
This objection to Berkeley put another
way: ontological categories
• Berkeley is confusing thoughts and what the
thoughts represent or are about.
• Take Hylas’s tree, existing unperceived.
– A thought of the tree is clearly not mind-independent.
– But what the thought is about, or of, or represents, is
not the same thing as the thought – thoughts and
things are in different ontological categories.
• So even if a thought of the tree is mind-
dependent, what the thought is of could perfectly
well be mind-independent.
Berkeley’s account of perception
Or: why are our perceptions consistent?
• (Ideas) of physical objects must be caused by
either ideas, my own mind, another’s mind.
– Ideas can’t cause anything as they need minds to
– I don’t control most of my ideas.
– So another mind must be causing my ideas.
– These ideas are pretty complicated. God is the
only entity complex enough to explain these
Issues with Idealism
• it leads to solipsism
• it does not give an adequate account of illusions
• it cannot secure objective space and time
• whether God can be used to play the role He
Homework: Investigate each of these issues. Write
a short paragraph about each outlining them.
Objection 1: It leads to solipsism
• Solipsism defined: we can have no objective evidence of the existence of
any other minds than our own.
• This solipsism arises from Berkeley’s claim – as a good empiricist – that we
can make no claim that anything exists unless we can have direct
experience of that thing.
– So we can have no direct experience of matter it does not exist.
– Yet we can have no direct experience of any minds other than our own
other minds do not exist.
• Berkeley’s response to this objection would probably focus on the notion
– as minds we have an idea of what other minds might be like (objection: how
can we know this notion to be accurate, given that we are generalising on the
basis of the experience of one mind alone…)
– our perceptions aren’t controlled by our minds so originate elsewhere, and
are so complex that only God can ultimately explain them (objection: this
might demonstrate at best that God exists, but no more)
Russell: The Problem of Solipsism
Other people are represented to me by certain sense-data, such as the sight
of them or the sound of their voices, and if I had no reason to believe that
there were physical objects independent of my sense-data, I should have no
reason to believe that other people exist except as part of my dream. Thus,
when we are trying to show that there must be objects independent of our
own sense-data, we cannot appeal to the testimony of other people, since
this testimony itself consists of sense-data, and does not reveal other
people's experiences unless our own sense-data are signs of things existing
independently of us. We must therefore, if possible, find, in our own purely
private experiences, characteristics which show, or tend to show, that there
are in the world things other than ourselves and our private experiences.
In one sense it must be admitted that we can never prove the existence of
things other than ourselves and our experiences. No logical absurdity results
from the hypothesis that the world consists of myself and my thoughts and
feelings and sensations, and that everything else is mere fancy.
Objection 2- Illusions and Hallucinations are not
• Realist theories of perception have a strong account of why it is that
illusions and hallucinations exist.
– What is this account? (Perception is of what is external to the mind,
Hallucination of what is internal to ie.
– Does Idealism have recourse to the same account?
• Idealism does not have recourse to the appearance/reality distinction.
• Illusions: the idealist view
– Bent pencils (in water) are bent.
– And yet are not when they are removed.
– So illusions are hard to account for.
• Hallucinations: the idealist view
– Hallucinations are imaginary, yet not voluntary.
– We can tell we’re having them because they are unclear, and inconsistent with
our other senses.
– But Berkeley can offer us no deeper explanation of why we have them (and
the realist can)
Objection 3: Objective space and time are not
• Realist theories of perception have a strong account of why it is that
time and space are objective.
– What is this account?
– Does the idealist have recourse to it?
• In contrast, the idealist says that space and time only exist in the
space of individual experience.
– So no two people ever see the same things: space varies according to
– And individual time-sense is widely variant.
• Berkeley’s likely reply: our perceptions are copies of ideas of things
in God’s mind. Regularities and consistencies in our shared
perception of the world arise because God’s ideas are consistent
(except in most of the Old Testament…etc…)
Objection 4: can God be used to play the role he
• What role does God play within Berkeleian idealism?
• Is the introduction of God satisfactory?
• Berkeley infers God’s existence because
– Objects are only ideas yet are consistent.
– Our perceptions are infinitely varied and so must be produced by a powerful
– We know our own minds and can imagine a mind more powerful therefore.
– our experience of the world is very limited, and limited to our own minds
– It is changeable (whereas God’s view of things is not)
– We experience pain and other limitations (and God does not)
• A theological response:
– We perceive copies of ideas in God’s mind.
– God does not so much perceive the world but maintain it perfectly in His
understanding, simultaneously. He knows but does not feel our pain.
God in the Quad: odd
There was a young man who said "God
Must find it exceedingly odd
To think that the tree
Should continue to be
When there's no one about in the quad."
"Dear Sir: Your astonishment's odd;
I am always about in the quad.
And that's why the tree
Will continue to be
Since observed by, Yours faithfully, God."