Hylas’s Accusations
Philonous “professes an entire ignorance of
all things [and] advances such notions as
are repugnant to plain and commonly
received principles.” (p.8)
Philonous maintains “the most extravagant
opinion that ever entered into the mind of
man, to wit, that there is no such thing as
material substance in the world.” (p.8)
Philonous “denies the reality and truth of
things.” Specifically, he “distrusts the
senses, denies the real existence of
sensible things, and pretends to know
nothing of them.” (pp.9-10)
Philonous’s Project
Show that Hylas’s belief in the existence of
external, independently existing bodies
drives Hylas into scepticism and paradox
while Philonous’s view that all that exists is
minds and their ideas is actually consistent
with commonly received principles
Hence, that it is Hylas’s view that actually
deserves to be considered extravagant.
Philonous is the one who is in a position to
affirm the existence of sensible things
(ideas) while it is Hylas who is forced to
confess that he knows nothing of the
sensible things (externally and
independently existing bodies) he believes
A preliminary point
Someone who denies the existence of
body* is not on that account to be
considered a sceptic.
(Berkeley does not just think that the
existence of body* is not provable. He
thinks there can be no such thing.)
* Here “body” means something considered to exist
outside of all minds and independently of being
Berkeley does not deny the existence of “body”
considered as sensible things.
Philonous’s Opening Move
What is a sensible thing?
Hylas’s Reply
A thing that is immediately perceived by the
So a colour, sound, thing that is hot
or heavy.
Not the cause of these things.
(Hylas starts off expressing a commitment
to “naive realism”)
Sensible things are nothing other than the
sensible qualities or combinations of
sensible qualities: light, colours, figures,
sounds, tastes, smell, and tangible
So if you take away all sensible qualities no
sensible thing remains.
Philonous’s Thesis
(esse est percipi)
A sensible thing can only exist insofar as it
is perceived.
Arguments for “esse est percipi”
 Identification of sensible objects with
pains and pleasures
Pain and pleasure are states of sentient beings.
They do not exist apart from being perceived or
outside of minds.
But a very great degree of heat just is a form of
pain, …
… a more moderate degree just is a form of
… a yet less degree is a lesser pleasure, …
… and an insensible degree is insensible
This same identification holds for smells, and
tastes, which are all either pleasant or unpleasant
and so forms of pleasure & pain.
Arguments for “esse est percipi,” cont.’d
 Perceptual relativity
No object can have contrary states at the same
But the same object can be felt to be both hot
and cold at the same time.
(The same holds for tastes, smells, colours,
and magnitudes)
So these qualities must be states of the
percipient rather than of some independently
existing object.
Arguments for “esse est percipi,” cont.’d
 Causal parity
(an “ad hominem” argument that might otherwise appear to be
inconsistent with Berkeley’s principles)
No one thinks that the sensation caused by a pin
dividing the flesh is in the pin.
By parity of example, no one should think that the
sensation caused by an object affecting a sense
organ is in the object.
 e.g., sound sensations and undulations
in the air
 e.g., sensations of colour and waves or
particles of light
An objection
Sensible qualities may be considered in two
 as they are perceived by us
 as they are in bodies
As they are perceived by us, they are
degrees of pleasure or pain.
But as they are in bodies they are not.
Sensible things are things immediately
perceived by the senses, not the causes of
those immediate perceptions.
Moreover, there is no resemblance
between the sensible qualities and their
supposed causes.
So sound causes cannot be acute or grave, loud
or soft; colour causes cannot be bright or dark,
red or green.
And sound causes, being shapes (waves) are not
the sort of things that can be heard, but only the
sort of things that can be felt or seen.
While colour causes turn out to be invisible
motions and figures rather than anything that
we actually see.
Insisting that these things are “sounds” or
“colours” brings us into conflict with
common sense.
A further objection
Even if we grant that some sensible
qualities (the “secondary”) only exist in us
and only exist when they are perceived,
there are other, “primary” qualities that exist
in external, unthinking bodies.
Problems with Primary Quality Realism
 Perceptual relativity arguments are as
effectively employed against the mindindependent existence of the primary
qualities as the secondary qualities.
 The primary qualities cannot be
conceived to exist apart from the
(So if the secondary qualities are granted to exist
only in the mind and only when perceived, the
primary must exist only in that way as well.)
A Further Objection
Though the act of perceiving may not exist
outside of the mind, the object perceived by
means of this act may exist outside the
The mind can only be said to act insofar as
there is volition involved.
But in perception there is no volition.
So the so-called “act” of perceiving turns
out to be something that the mind does not
do and so, on the account, it could exist
outside of the mind (though this is absurd).
Worse, the so-called “object” of perception
could not possibly exist outside of the mind
in many cases, e.g., the perception of pain.
So the attempt to divide perception into an
act that must exist in the mind from an
object that must exist outside of it is
Yet another Objection
Sensible things are all merely modes or
But it is inconceivable how modes or
qualities could exist on their own, without
inhering in some material substratum or
Substance and substratum are not sensible
Neither can they be relative notions, implied
by the existence of sensible things.
Because we have no idea what we
mean when we talk about these
Neither could the group of sensible qualities
mutually support one another.
Because it has already been
established that each sensible
quality could not possibly exist
outside of a mind (whether combined
with others or not).
Berkeley’s “Master Argument”
It is impossible to conceive of something
existing unconceived.
Because when you conceive of
something existing unconceived you
yourself conceive that thing.
[or you conceive nothing at all, in
which case you still don’t
conceive anything existing
So, nothing can legitimately be supposed to
exist apart from being conceived.
(Maintaining that something does exist
unconceived when you cannot even so
much as conceive or imagine something
to exist unconceived is unacceptable.)
Another Objection
We see things at a distance from us.
So things must exist outside of us and
hence independently of being perceived.
 We perceive things as being at a
distance from us in dreams, even
though they are not outside us
 What we see at a distance looks
different close up. So what we were
seeing when at a distance cannot have
been the (then) distant object but must
have been something in us.
 Someone born blind and newly made to
see would not perceive things as being
at a distance
 Since distance is a line turned endwise
to the eye, the length of the line (and
hence the distance) cannot be
 It has been shown that colours do not
exist outside of the mind, yet they
appear as being at a distance.
A further objection
The ideas or sensible things we
immediately perceive are pictures of
external things, and we perceive the
external things mediately by perceiving
these ideas.
Before something can be seen as a picture
of something else, you need to have some
prior acquaintance with that other thing.
But the question at hand is what sensory
experience, memory or inference could give
us that prior acquaintance and so put us in
a position to legitimately suppose that there
are material things resembling our
Hylas’s Last Resort
The existence of external, independently
existing bodies resembling our ideas is at
least possible.
(The “Likeness Principle”)
It is not, because nothing can be like an
idea but another idea …
e.g., nothing invisible can be like a
colour, nothing inaudible like a sound
… because nothing we find in our ideas can
be conceived to be the sort of thing that
could exist outside of a mind.
Hylas: Upon inquiry, I find it impossible for
me to conceive or understand how anything
but an idea can be like an idea. And it is
most evident, that no idea can exist without
the mind.
Philonous: 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