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The Nature of Perception
Foster, John
Fellow and Tutor in Philosophy, Brasenose College, Oxford
Abstract:
Within the framework of a realist view of the physical world, there are two
general theories of the nature of perception. The first is strong direct realism (SDR). This
accepts a realist view of the physical world, and claims that our perceptual access to this
world is psychologically direct. The second is the broad representative theory (BRT).
This too accepts a realist view of the world, but claims that perceptual contact with
physical items is always psychologically mediated, i.e. it is constituted by the
combination of the subject's being in a more fundamental psychological state, which is
not in itself physical-item perceptive, and certain additional facts. SDR cannot provide a
satisfactory account of the phenomenal content of perception and how such content
features in the securing of perceptual contact. BRT cannot explain how we can have
genuine perceptual access to the physical world at all. In the face of this dilemma, the
only way of providing a satisfactory account of perception is by abandoning the
assumption of physical realism and adopting an idealist view of the physical world. This
view can, in any case, be established as correct by independent arguments.
Abstract 2
: Let us provisionally assume a realist view of the physical world, which
takes the world to be mind-independent and metaphysically fundamental. Within the
framework of this assumption, there are two general theories of the nature of perception.
Let us say that a subject Φ-terminally perceives a certain physical item if and only if he
perceives that item, and there is no other physical item such that his perceiving of this
second item mediates his perceiving of the first. Then one of the two theories endorses a
realist view of the physical world, and claims that, when someone Φ-terminally perceives
a physical item, his perceptual contact with that item is something psychologically
fundamental. I call this ‘strong direct realism’ (SDR). The other theory also endorses a
realist view of the world. But its claim is that, whenever someone perceives a physical
item (and even when the perceiving of this item is Φ-terminal), his perceptual contact
with it is psychologically mediated, i.e. it is constituted by the combination of his being
in some more fundamental psychological state, which is not in itself physical-item
perceptive, and certain additional facts that do not involve anything further about his
current psychological condition. I call this the ‘broad representative theory’ (BRT). The
first issue we face, then, is: which of these two theories should we accept?
Keywords: direct realism, mediation, mind-independent, perception, physical world,
realism, representation
Contents
Part One The Reshaping of the Issue 1
Part Two An Examination of Strong Direct Realism 19
Part Three The Mediating Psychological State 93
Part Four The Problem of Perception 196
Part Five The Idealist Solution 244
Part One The Reshaping of the Issue
1 The Traditional Issue
What is the nature of perception—the sensory perception of items in the physical world
by human subjects?
By tradition, there are three general theories. First, there is
direct realism
. This accepts a
realist view of the physical world: it takes the physical world (the world of physical space
and material objects) to be something whose existence is logically independent of the
human mind, and something which is, in its basic character, metaphysically fundamental.
And, within this realist framework, it takes our perceptual access to the physical world to
be direct. Second, there is the
representative theory
(or
representative realism
). This too
accepts a realist view of the physical world. But it sees this realism—in particular, the
claim of mind-independence—as putting the world beyond the reach of direct perception.
Thus, in place of the claim that our perceptual access to the physical world is direct, it
insists that the perceiving of a physical item is always mediated by the occurrence of
something in the mind which represents its presence to us. Finally, there is
idealism
. This
agrees with the representative theory in holding that direct perceptual awareness does not
reach beyond the boundaries of the mind, but manages to combine this with the insistence
that our perceptual access to the physical world is nonetheless direct. What enables it to
combine these seemingly irreconcilable views is that it abandons physical realism. Thus
it takes the physical world to come within the reach of direct perceptual awareness by
taking it to be something which is logically created by facts about human sensory
experience, or by some richer complex of facts in which such sense-experiential facts
centrally feature.
Of these three traditional positions, the idealist option is likely to strike us, initially, as
just absurd. This is not merely because it is an affront to ‘common sense’—an outright
rejection of something which we ordinarily take for granted. It is also, and more
importantly, because it seems that our
end p.1
very concept of the physical world requires it to be something external to, and
ontologically independent of, the human mind. For reasons which will emerge, I think
that such a dismissal of idealism is too hasty. But, for the time being, I am going to put
the idealist option on one side, and, in company with almost all other current
philosophers, look at the issue of perception in the framework of physical realism.
Within this realist framework, the traditional debate focuses on the issue between direct
realism, which takes our perceptual access to the physical world to be direct, and the
representative theory, which takes it to be representationally mediated. However, before
we can properly deal with this issue, we need to pause to reshape it. For it turns out that
there are two crucially different ways in which the claim of direct access can be
interpreted; and, for each interpretation, there is a corresponding version of the
representative theory to stand in contrast. In other words, what poses as a unitary issue,
turns out, on closer examination, to be the conflation of two distinct issues—between two
distinct forms of direct realism and the correspondingly distinct forms of the
representative theory. We obviously cannot hope to make any progress in our
investigation until we have brought the two issues to light and decided the manner in
which we are going to address them.
2 The Two Interpretations
I
We must start by getting clear about the precise point at which the different
interpretations of the direct-access claim arise. And, as a first step, I need to introduce
and explain two key notions: that of
constitution
and that of
perceptual mediation
. I shall
take these in turn.
Let us say that a fact F is
constituted by
a fact F', or by a set of facts α, if and only if (1) F
obtains
in virtue of
the obtaining of F' (the obtaining of the members of α) and (2) the
obtaining of F is
nothing over and above
the obtaining of F' (the obtaining of the
members of α). The relation of
obtaining in virtue of
is to be understood as necessarily
asymmetric, so that we cannot envisage a case in which F obtains in virtue of the
obtaining of F' and F' obtains in virtue of the obtaining of F. This means, in particular,
that we cannot speak of a fact as constituted by itself (though, trivially, its obtaining is
nothing over and above its obtaining); and, in effect, it means that we cannot speak of a
fact as constituted by a set of facts which contain
end p.2
it. I am using the term ‘fact’ in what I take to be its standard philosophical sense, to
signify an aspect of how things are. I could equally well have used the expression ‘state
of affairs’; my preference for ‘fact’ is only that it is shorter.
The definition of constitution allows it to occur in two forms, as either a relationship
between two facts or a relationship between a fact and a set of facts. In effect, the
distinction here is between the case where the constitutive base comprises a
single
fact
and the case where it comprises a
plurality
of facts. I say ‘in effect’, because, technically,
a set of facts could contain only one member. But to envisage a case in which a fact F is
constituted by the set whose sole member is a fact F' is to envisage a case which would
be more naturally described as one in which F is constituted by F'.
It is easy to find examples of both forms of constitution. A range of clear-cut cases of
single-fact constitution is provided by the relationship between the instantiation of a
generic (determinable) property and the instantiation of some specific (determinate) form
of it. Thus if an object is scarlet, then the fact of its being (generically) red is clearly
constituted, in the relevant sense, by the fact of its being (specifically) scarlet: the generic
colour-fact obtains in virtue of, and its obtaining is nothing over and above, the obtaining
of the more specific. A range of clear-cut cases of multi-fact constitution is provided by
the relationship between the weight-relationship between two objects and their individual
weights. Thus if John weighs twelve stone and Mary weighs ten stone, the fact of John's
being heavier than Mary is clearly constituted, in the relevant sense, by the combination
of the fact that John weighs twelve stone and the fact that Mary weighs ten stone: their
weight-relationship obtains in virtue of, and its obtaining is nothing over and above, the
combination of the separate weight-facts about them. Any case of multi-fact constitution
can, of course, be automatically recast as a case of single-fact constitution by simply
replacing the plurality of facts by their conjunction; or at least this can be done if the
plurality is finite. But all this shows is that a case of single-fact constitution is only
interestingly
of a single-fact form if the single fact in question is
not
explicitly or
implicitly conjunctive in that way.
Where a fact is constituted by a plurality of facts, I shall also speak of it as ‘breaking
down’ or ‘decomposing’ into those facts. So, in the example above, the weight-
relationship between John and Mary (John's being heavier than Mary) can be said to
break down
, or
decompose
, into the facts about their individual weights—the facts which
in combination constitute that relationship.
Two other things should be noted. First, there are cases of
constitutive
end p.3
overdetermination
, where a single fact is separately constituted in two ways. For
example, given any pair of facts, that p and that q, the disjunctive fact that either p or q is
separately constituted by each of these facts on its own. Second, it will be convenient to
construe the relation of
obtaining in virtue of
, as it features in the definition of
constitution, in a way which excludes forms of redundancy in the constitutive base. Thus
if F obtains in virtue of the obtaining of F', then we are not to speak of F as obtaining in
virtue of the obtaining of the conjunction of F' and some further fact, or in virtue of the
obtaining of some plurality of facts which includes F'. And if F obtains in virtue of the
obtaining of the members of α, we are not to speak of it as obtaining in virtue of the
obtaining of the members of some larger set which includes α. This means, in particular,
that, in cases of constitutive overdetermination, we are not to speak of the fact which is
doubly constituted as also constituted by the combination of the facts, or sets of facts,
which are separately constitutively involved.
With the notion of constitution in place, I can now explain the notion of
perceptual
mediation
. It often happens that the perceiving of one thing is wholly channelled through
the perceiving of another. This occurs when, for some subject S, time t, and items x and
y,
(1)
S perceives x at t;
(2)S perceives y at t;
(1)
S perceives x at t;
(3)
S's perceiving of x at t breaks down into (is constituted by the combination of) his
perceiving of y at t and certain additional facts;
and
(4)
these additional facts do not involve anything further about S's perceptual condition at
t (anything over and above what is already covered by S's perceiving of
y
). In other
words, in combining with the fact of S's perceiving of y, they do not add further
perceptual facts, about S at t, to the constitutive base.
It is this phenomenon that I call ‘perceptual mediation’; and, in cases where it obtains, I
speak of the perceiving of the relevant y as
perceptually mediating
the perceiving of the
relevant x, and the perceiving of x as
perceptually mediated by
the perceiving of y.
Perceptual mediation can assume a number of forms (or putative
end p.4
forms) according to the nature of the additional facts involved—the facts which combine
with the perceiving of the one item to constitute the perceiving of the other. We shall be
looking at these different forms in due course. At present, it is best to confine our
attention to a very simple type of case. Thus suppose Pauline is looking at an apple on the
table. She sees the apple (A), and, in that sense, sees the
whole
apple. But she does not
see
the whole of
(
every part of
) A: the only part which is strictly visible to her is a certain
portion (P) of A's surface. In consequence, her seeing of A breaks down into (is
constituted by the combination of) her seeing of P and the fact that P is a portion of A's
surface. And this means that her seeing of P perceptually mediates her seeing of A in the
sense defined. We can take the example one stage further. The relevant portion of A's
surface, like A itself, is a temporal continuant—something which persists through time.
But, at each moment when Pauline sees this portion, she sees it, not as it is at the various
stages of its history, but only as it is
at that moment
—or strictly, given the time it takes
for light to travel from the surface of the apple and get visually registered, she sees it as it
was at a
fractionally earlier
moment.
1
This means that, just as Pauline's seeing of A is
perceptually mediated by her seeing of P, so, at any particular moment, her seeing of P is
perceptually mediated by her seeing of a certain momentary stage (time-slice) of it. For it
means that, at each such moment, her seeing of P breaks down into (is constituted by the
combination of) her seeing of the relevant momentary item and the fact that this item is a
momentary stage of P. Obviously, we could apply this same two-stage analysis to
any
instance of seeing a material object—to yield any number of further cases in which the
seeing of the whole object is perceptually mediated by the seeing of a part, and the seeing
(at a particular moment) of this part is perceptually mediated by the seeing of a time-
slice.
In considering cases of perceptual mediation, it must always be borne in mind that the
relationship holds between
facts
of perceiving, not
acts
(concrete events) of perceiving.
Thus when we say that a subject's perceiving of one thing is perceptually mediated by his
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