EPISTEMOLOGY- lec 5 Flashcards
The traditional claim that perception does not provide immediate justification for
perceptual beliefs
There is a long tradition of treating our justification for everyday beliefs based on perception as
dependent on our justification for beliefs of other kinds (‘mediated’)
A coherentist version of this dependence claim
Perceptual beliefs are justified insofar as they fit
together with beliefs of other kinds (for example, beliefs based on memory; beliefs based on testimony; beliefs arrived at by scientific theorizing) into a coherent picture of what the world is like
Note that the coherentist version of this dependence claim opens up the possibility that scientific
advances might undermine the status as justified of everyday perceptual beliefs
A foundationalist version of this dependence claim
Perceptual beliefs are justified because we are justified in
believing that our perceptual information processing is
reliable, and, given justification for this belief, we can
arrive at justification for perceptual beliefs by inferences
like this:
P1 It perceptually seems to me that there is something square there.
[Premiss about perceptual appearance.]
P2 If it perceptually seems to me that X, it is very probable that X.
[Reliability premiss.]
C It is very probable that there is something square there. [Conclusion]
Note that someone advocating the foundationalist version of the dependence claim is stuck
looking for a reason to accept P2 (the reliability premiss) which does not already presuppose that
beliefs formed by uptake from perceptual experience are justified.
Arguments for the traditional claim
2.i The indiscriminability of ‘good case’ from ‘bad case’ perceptual experiences
One argument for the traditional claim begins with the observation that ‘good’ cases of
perceptual experience (seeing a tomato in ordinary lighting in circumstances where your perceptual system is functioning normally so the red tomato looks red) are subjectively indistinguishable from ‘bad’ cases (having an illusion as of something red when in fact you are
looking at something white; having an hallucination as of something red when in fact there is
nothing there at all):
1 I am not in a position to tell whether the perceptual experience I am now having is a good case
(veridical) experience of a red tomato on the table or a bad case (illusory or hallucinatory
experience): even if I am having a ‘good case’ perceptual experience, my experience could be
just the same if I were hallucinating or suffering an illusion.
But
2 If perceptual experience alone is to justify me in believing that there is a tomato on the table it
must rule out all possibilities in which there is not a tomato there.
So
3 Perceptual experience alone cannot justify me in believing that there is a tomato on the table.
Therefore
4 If I am justified on the basis of perception in believing that there is a tomato on the table, my
justification must involve some additional factor as well as the perceptual experience.
5 The only candidates to provide the required additional factor are my other beliefs.
So
6 If I am justified on the basis of perception in believing that there is a tomato on the table, my
justification is mediated justification (it involves not only my perceptual experience, but some or
all of my other beliefs as well)
he old empiricist view of what perceptual experience delivers
Empiricism’ is the view that all knowledge and the meanings of all words are based in
perceptual experience.
If you are going to develop an account of knowledge (or meaning) within an empiricist
framework, you need an account of what perceptual experience delivers. The traditional
empiricist account of what perceptual experience delivers treated perception as a source of only a
very thin informational signal – which could then be treated as data on the basis of which the
subject was to be regarded as constructing a theory of what the world outside the mind is like.
According to one version of this view, perceptual experience delivers a pattern of qualitative
features (‘red square’; ‘blue circle’…) from which the theory of the external world must be built.
[Locke, Berkeley, Hume, Russell, Ayer (criticized by Strawson in our reading).]
According to another version, our perceptual systems deliver patterns of stimulation (Quine says
‘surface irritations’ or ‘ocular irradiations’) , and the task for the epistemologist and theorist of meaning is to
explain how we get from these patterns of stimulation to a system of beliefs which we take to be
‘about’ things in the world around us.
According to each of these versions of the traditional empiricist standpoint, perception on its
own does not present the world around us as containing ordinary middle sized objects: the belief
that there is a tomato in front of you stands to the perceptual experience that gives rise to it as an
element of a theory stands to the data that the theory is introduced to explain. But we saw last
time that justification in scientific theory-construction is holistic –
any factor that contributes to justifying belief in one of the statements of a scientific theory does
so only in relation to an array of other beliefs, so that the factor really contributes to justifying a
whole network of beliefs – the new belief together with the background array.
So if coming to believe that there is a tomato in front of you on the basis of perception is part of
your ongoing activity of constructing a theory to explain your evolving stream of sense experience, your justification for the belief is mediated by the background beliefs that make up the relevant part of your theory
Arguments against the traditional claim
Though it is very important in the history of epistemology, there are good reasons to reject the
traditional claim that perception can only ever provide mediated justification for everyday
perceptual beliefs.
The argument from what is more certain
1 Our everyday perceptual beliefs are justified partly on the basis of other beliefs. [Assumption
for reductio]
2 A belief cannot impart more certainty on beliefs it contributes to justifying than it has itself.
3 We are more certain of our everyday perceptual beliefs than we are of the beliefs that might be
claimed to contribute to justifying them (for example the belief that, in general, our perceptual
information processing delivers reliable results).
4
1, 2, and 3 are inconsistent, and it is 1 that should be rejected.
5 An everyday perceptual belief is justified without the contribution of other beliefs
The argument from limitations in our cognitive capacities
1 The traditional dependence claim treats forming an everyday perceptual belief as a cognitively
demanding procedure in which the subject moves to the perceptual belief on the basis of other
beliefs that contribute to its justification.
2 Our brains have information processing power N [actual value to be determined by cognitive
science].
3 We form perceptual beliefs with such frequency and rapidity that if this traditional claim were
right, our brains would have to have information processing power N ́ 10i [actual gap between
this figure and the figure in 2 to be argued about; what matters is just that the gap is big].
So
4 The traditional dependence claim should be rejected.
The (empirical) falsity of the old empiricist view of what perception delivers
the old empiricist view of what perception delivers has been overturned by advances in
scientific understanding of the perceptual system.
If the traditional claim is false, what should we say instead?
Many contemporary philosophers thinking about how perceptual beliefs are justified endorse
some form of defeasible justification view:
Definition: ‘defeasible’ justification for a belief is justification that is consistent with the belief’s
falsity, and that may be overturned by subsequent evidence.
According to a defeasible justification view,
a) everyday perceptual beliefs are justified in virtue of being formed in response to perceptual
experience, and without mediation by other beliefs; where
b) this initial (‘prima facie’) justification is consistent with the falsity of the belief, and may be
overturned by subsequent evidence.
So, for example your belief that there is a red round thing on the table in front of you, formed in
response to perception in the ordinary way, is justified in virtue of being formed in response to
perception, but this justification might be overturned by subsequent evidence, for example,
evidence that the lighting is bad or that your perceptual system is not working properly or….
Someone advocating this kind of view is rejecting 2 in the argument of 2.i.
NOTE – SOMEONE PROPOSING THIS VIEW STILL OWES US AN ACCOUNT OF HOW PERCEPTUAL
EXPERIENCES JUSTIFY BELIEFS.
QUESTION – IF JUSTIFICATION FOR AN EVERYDAY PERCEPTUAL BELIEF IS ONLY DEFEASIBLE
JUSTIFICATION, AND A TRUE BELIEF THAT COUNTS AS KNOWLEDGE IS NOT JUST LUCKILY TRUE,
HOW CAN A ( JUSTIFIED AND TRUE) EVERYDAY PERCEPTUAL BELIEF COUNT AS KNOWLEDGE?
