Reality Consists of Ideas
Classic Philosophical Questions Part 6 - Metaphysics
George Berkeley, from Three Dialogues Between Hylas and Philonous
Kem Stone - 11 February 2008
In almost three centuries since the bishop George Berkeley argued that reality is made up solely of ideas and that
material substance does not really exist, nobody has been able to conclusively refute him.  This is because his
arguments rest on something so fundamental to human experience that to deny it is a blatant absurdity—that
everything we know is known through the mind, in the form of ideas.  Whether material substance exists or not
our awareness of the outside world comes to us through subjective experience and
only subjective experience.  
We can have no understanding of the world except through the ideas implanted in our conscious minds through
sensation and reflection, which gives rise to the idea that this is perhaps all that is needed.  God could have
created the world in such a way that only minds and ideas exist, without exerting the extra effort of actually
creating material substances to stand between the creator and perceiver.  In this text, Berkeley shows how the
apparent certainty of the existence of the outside world is not certain at all, and that all we can be sure exists are
the ideas in our minds.

The dialogue begins with Hylas (meaning “matter”) accusing Philonous (meaning “Friend of Mind”) of espousing
the most extreme form of scepticism in a previous conversation, in which he had asserted that there is no such
thing as material substance.  Philonous rejects this characterisation, asking Hylas to clarify what he means by
scepticism.  Hylas replies that a sceptic is one who doubts of everything, but Philonous points out that he is not a
sceptic because a sceptic would express doubt on both sides of an issue whether affirmative or negative, while
Philonous firmly embraces the negative side of the question of material substance.  Amending his definition, Hylas
pronounces that a sceptic is he who denies the reality and truth of things, which opens the door for Philonous to
examine the opinion of Hylas and show that his is actually the position that leads to scepticism.

Philonous first asks what is meant by “sensible things” to which Hylas replies that he means nothing more than
those things which are perceived by the senses.  A distinction is then drawn between things that are perceived
immediately and those perceived mediately, or through intervention.  For instance, in reading a book it is the
letters that are immediately perceived, while the words themselves and the ideas they suggest are perceived after
some reflection on the part of the mind.  Once this clarification is made, Hylas pronounces that, “by ‘sensible
things’ I mean only those which are perceived by sense, and that in truth the senses perceive nothing which they
do not perceive immediately, for they make no inferences” (375).  Philonous asks whether the reality of sensible
things consists in being perceived, or whether it is distinct from perception and bears no relation to the mind.  To
this, Hylas’ reply is the opposite of the position that Berkeley, through Philonous, argues for: to exist and to be
perceived are two different things.

The first challenge that Philonous offers to this notion is the idea of heat, which Hylas insists must exist absolutely
and distinctly from the mind which perceives it.  Through a series of questions, Philonous establishes that the real
existence of heat must be equally compatible to all its degrees, and that the most intense degree of heat is a very
great pain.  Hylas can not deny this, but he runs into trouble when he also insists that material substance is
senseless, as it is a problem to say that a fire contains pain and yet feels no pain itself.  Hylas tries to save his
argument by claiming that heat and pain are distinct—that pain is merely a consequence of heat, which really exists
in the fire.  Philonous, however, does not allow him this distinction, as both the heat and the pain are experienced
immediately, as one simple sensation.  “Seeing therefore they are both immediately perceived at the same time,
and the fire affects you only with one simple or uncompounded idea, it follows that this same simple idea is both
the intense heat immediately perceived and the pain; and, consequently, that the intense heat immediately
perceived is nothing distinct from a particular sort of pain” (376).  Hylas must concede this point.

Philonous then asks Hylas to try to conceive of any sensible pain or pleasure abstracted from the idea of heat,
cold, taste, smell, and so on.  Hylas admits that he begins to suspect that a great heat cannot exist but in a mind
perceiving it.  To further drive the point home, Philonous asks Hylas to suppose that one of his hands is hot and
the other cold, and both are placed at once into the same vessel of water in an intermediate state.  The water will
seem cold to one hand, and hot to the other.  Yet to suggest that the water is actually both hot and cold at the
same time is an absurdity.  Thus, the proposition that sensible things such as heat and cold, pleasure and pain,
exist independently from minds is proven false.

Hylas, however, is not ready to concede that
nothing can exist without the mind, so he offers the proposition that
certain qualities must exist independently within external objects, such as colours.  Every object, he insists, actually
has the colour we see in it.  Philonous dismisses this notion by establishing that nothing is visible but what we
perceive by sight, and that colour is therefore a sensible quality that cannot exist without the mind, just as heat,
cold, and pain, and the other sensations that he had just established are dependent upon perception for their
existence.  “In saying ‘each visible object has that colour which we see in it,’ you make visible objects to be
corporeal substances, which implies either that corporeal substances are sensible qualities or else that there is
something besides sensible qualities perceived by sight; but as this point was formerly agreed between us, and is
still maintained by you, it is a clear consequence that your corporeal substance is nothing distinct from sensible
qualities” (378).

Unwilling to concede this point so quickly, Hylas accuses Philonous of sophistry, and insists that colours actually
do exist in their objects.  Philonous then asks Hylas whether the beautiful red and purple he sees in the clouds
really exist in them, to which Hylas admits that these are only
apparent colours.  Asked to clarify his meaning,
Hylas replies, “Those are to be thought apparent which, appearing only at a distance, vanish upon a nearer
approach” (378).  By this criterion, however, it must be admitted that all colours are merely apparent, as a
microscope often reveals different colours in an object than those perceived through unassisted sight.  The colours
we see not only in clouds, but in
all objects, tend to vanish upon closer inspection.  Hylas presses this point no
further, and admits that all
secondary qualities such as colours, sounds, tastes, and the like, have no existence
without the mind.

Up to this point, all but the strictest materialists would probably concede along with Hylas that the qualities that
have thus far been mentioned do not exist except in the mind of a perceiver.  However, most of us are not willing
to go the next step and say that even primary qualities such as extension, figure, solidity, and motion also do not
really exist in bodies.  Hylas puts this challenge to Philonous, standing by the position that primary qualities are
inherent in corporeal objects.  Philonous insists that the same arguments used against the real existence of
secondary qualities can be used against these.

Berkeley shows that even a quality such as size, which is thought to be independent of perception, is actually
dependent upon the perspective of the perceiver.  The first example Philonous gives is that of a very small insect:
“A mite therefore must be supposed to see his own foot, and things equal or even less than it, as bodies of some
considerable dimension, though at the same time they appear to you scarce discernible or at best as so many
visible points?” (379).  The foot of a mite is nothing but a speck to a human observer, but to the mite itself it has
considerable size.  Even a single observer, as he approaches or recedes from an object, will perceive the same
object as having different sizes.  Moving around an object, he will perceive it to have different dimensions from
each angle at which he views it.  “Is it not the very same reasoning to conclude there is no extension or figure in an
object because to one eye it shall seem little, smooth, and round, when at the same time it appears to the other
great, uneven, and angular?” (380).  These arguments show that qualities such as size and figure, just like heat and
cold or colour, are merely apparent and exist only as ideas in the mind.

Hylas acknowledges that because he is nothing more than a thinking being affected by sensations, he cannot
conceive of the nature of a substance abstracted from conception itself.  But he still holds firm to his opinion, and
tries to save his definition of “sensible things” by calling them modes and qualities supported by a
material
substratum
, without which they could not exist.  Examining this definition, Philonous asks whether the word
“substratum” is meant to mean that it is spread under the sensible qualities, which Hylas says is true.  This,
however, would entail that it has extension.  This is a problem because extension, it has already been
acknowledged, is a quality that exists only in the mind.  Thus the extension of the substratum would require
another substratum beneath it to support the extension of the first substratum, and this second substratum being
extended as well would require a third, and so on to infinity.

Hylas insists that Philonous is taking his meaning too literally.  “I do not mean that matter is
spread in a gross literal
sense under extension.  The word ‘substratum’ is used only to express in general the same thing with ‘substance’”
(381).  But Philonous simply asks whether the term “substance” means that it stands under sensible qualities as
well, and would thus be liable to the same absurdity.  Now completely frustrated, Hylas gives up and admits that
he no longer understands exactly what he means when he conceives of material substance, though he remains
unwilling to declare that it does not exist, because he can not conceive of how qualities could exist without the
support of actually existent material.

Philonous points out that when conceiving of material substance, Hylas is actually conceiving of something that
cannot be conceived, and asks whether material objects in themselves are perceptible or imperceptible.  Hylas
replies, “Properly and immediately nothing can be perceived but ideas.  All material things, therefore, are in
themselves insensible and to be perceived only by their ideas” (382).  This is a proposition that most of us would
agree with, but Philonous does not hesitate to question it.  He asks whether something sensible can really be like
something that is insensible, whether something that is invisible can be like a colour, or something inaudible can be
like a sound.  Though I and many others would now stand up to Philonous and insist that this is all quite possible,
Hylas concedes the point.

Finally, Philonous asks Hylas to consider whether he can conceive of anything at all existing without the mind, and
Hylas admits that it certainly seems that nothing but an idea can be like an idea, and that no idea can exist without
the mind.  Triumphant, Philonous declares, “You are, therefore, by your principles forced to deny the reality of
sensible things, since you made it to consist in an absolute existence exterior to the mind.  That is to say, you are a
downright sceptic.  So I have gained my point, which was to show your principles led to scepticism” (382).  
Though Hylas declares he is not completely swayed, he admits he can think of no further arguments.

And this is where the matter still stands today, three hundred years later.  We are not convinced by Berkeley’s
arguments because the existence of the external world seems so plain and obvious that to question it seems
absurd.  However, we find it impossible to prove that anything but ideas really exist.  This is, of course, nothing
special.  To prove the existence of
anything, as we have seen time and time again, is nearly impossible.  Even
when dealing with the world we see every day and the objects that are constantly presented to us, there is no
guarantee that it is all naught but illusion, a dream we can not wake from, or a virtual reality program we are all
trapped in.

Yet Berkeley’s triumph is not ontological as was his intent.  He came no closer to disproving the existence of
external objects than a materialist can come to proving their existence.  What Berkeley has shown, quite
conclusively, is that we can never
know whether external objects exist.  As an epistemological argument it is
sound, brilliant, and completely irrefutable.  All we know of are ideas, and therefore we cannot be certain that
anything but ideas exist.  But as an ontological argument it fails, because it has not established that something we
cannot
conceive of cannot exist.

That something other than an idea can be like an idea, that something invisible can be like a colour or something
inaudible can be like a sound, are propositions that any scientist today will readily accept.  All visible objects are
composed of infinitesimally small particles that themselves can not be seen, that can scarcely be
imagined.  A
sound is nothing more than vibrations in the air, these waves in themselves nothing like the idea produced by our
brain’s interpretation of them.  Even the electrical signals of the brain which give rise to the ideas are in themselves
nothing like the ideas themselves.  These things are certainly puzzling to think about, but this just happens to be the
curious way in which the world works.  Science continues to make progress under the assumption that a material
world exists, and while it can never be anything more than an assumption, Berkeley’s arguments give us no reason
to abandon it.