Tuesday, June 22, 2004

Objects of Perception

What are the objects of perceptual awareness? The intuitive answer is probably "physical objects" - we think our perceptions are perceptions of the world (Direct Realism). The Shallow Foundationalist relies on direct realism when he claims that perception can directly justify our beliefs about the external world.

The Argument from Illusion is meant to cast doubt on this. There are many ways our perceptions can play tricks on us - for example, objects half-immersed in water look bent. The real object is not bent though, so whatever it is that we are perceiving, cannot be the actual object. Instead, we merely perceive a mental object, or sense datum. The Deep Foundationalist insists that only beliefs about sense data (not the external world) can serve as foundational beliefs (though we might be able to infer from these to beliefs about the world).

This highlights the gap between appearance and reality, between evidence and truth, between what we experience and what is actually there. Our senses clearly do not provide us with infallible knowledge of the world. But it gets worse. For if all we perceive is sense data, not the world itself, then it would seem that our perceptions don't tell us anything about the outside world at all. We cannot justify beliefs about the external world solely from sense data.

We seem to have the following options:
1) Phenomenalism (anti-realism) - deny that the physical world exists. Minds and sense-data are all there is. The realist structures described by science are just a "useful fiction" which help us to predict the order within our experiences.

2) Representational Realism - Suppose we add in the additional assumption that our sense data are usually caused by, and resemble, real objects. That would then allow us to make justified inferences about the external world (not infallible ones, but at least generally reliable).

[Either way, by basing all justification on our subjective sense impressions, the deep foundationalist seems committed to the existence of a Wittgensteinian private language, which could be a problem.]

#2 seems preferable, but how could we possibly know whether the assumption it relies upon is true or not? This is really just the problem of skepticism all over again. We would seem to have to resort to some form of externalism, whereby justification for our beliefs is independent of our awareness of the justification (e.g. possible worlds externalism, or perhaps reliabilism - i.e. the belief must be caused by a reliable process in fact, whether we realise it or not).

Alternatively, the internalist could accept that perception/experience does not justify our beliefs after all. Instead, it causes beliefs to form in the first place. Where does the justification come from, then? We would have to give up on foundationalism, and accept coherentism instead: no beliefs are intrinsically or categorically justified. Instead, a belief is justified to the extent that it coheres with our other beliefs.

1 comment:

  1. [Copied from old comments thread]

    Richard, interesting blog! Thanks for your comments to my post. It's funny that our posts resemble one another (purely by coincidence).

    To my mind, there is something more to the justification of experience. It requires commitment. Commitment is an antecedent condition to belief. So, when someone says, "there's an antelope," the person is committed to the notion that visual perception is not now failing me. Is commitment a priori? hmmm...

    I've added you to my blogroll as well!
    Joe | Email | Homepage | 24th Jun 04 - 2:58 am | #


    Quick question. Have you read Putnam's latest (The Threefold Cord: Mind, Body, and World)? It deals with these questions directly, and takes a novel direct realist approach, arguing that the causal theory of perception is ultimately nonsense.

    Anyway, just thought I'd make the recommendation, if you haven't already read it.
    Anonymous | 27th Jun 04 - 10:53 pm | #


    Nope, sounds interesting though. I'll add it to my reading list. Thanks for bringing it to my attention
    Richard | Email | Homepage | 28th Jun 04 - 1:09 pm | #

    No problem. Like the blog. I put it on my regular rotation.
    Hunt | Email | Homepage | 28th Jun 04 - 2:05 pm | #


    The conclusion "it would seem that our perceptions don't tell us anything about the outside world at all" does not follow from the statement "if all we perceive is sense data, not the world itself".

    True, we do not experience the world directly, but the mechanisms by which we have indirect knowledge have evolved as we have evolved because they correspond to elements of the external world which are import for our survival.

    eg. the categories of Red and Green are mental constructs as they do not correspond to any discontinuities in the electro-magnetic spectrum. However, the Red/Green aspect of colour perception reflects our more fruitarian past where it was advantageous to discriminate between these two colours.

    We do not experience and process a random stream of sense data. This activity has honed to reflect our external world.

    You may be interested in Ramachandran's Reith Lectures - the Emerging Mind:


    neil | Email | 30th Jun 04 - 12:43 pm | #


    Neil, you're quite right, though you took my quote a little out of context. You'll notice that I later point out that realism can be saved if "we add in the additional assumption that our sense data are usually caused by, and resemble, real objects".

    But the skeptic would say we are not justified in making that assumption. Appealing to evolution won't do much good if the external world (and thus all evidence for evolution) is just an illusion
    Richard | Email | Homepage | 30th Jun 04 - 3:20 pm | #


    Apologies for not noting #2. Skepticism then becomes a form of solipsism since some of our percption faculties - face recognition for example - have been designed for the external reality of other people. If, for the skeptic, there is no external reality then there can be no other people (as well as no everything else).

    But as you suggest it is impossible to argue against a pure skeptic position, accept to threaten bodily harm - since as they would deny external reality they should have no objection.
    neil | Email | 30th Jun 04 - 4:29 pm | #


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