Posts on: Perception
Sensory information is centred. Right now, for example, my visual
system conveys to me that there's a red wall about 1 metre
ahead (among much else); it does not convey that Wolfgang
Schwarz is about 1 metre away from a red wall on 22 January 2026 at
12:04 UTC.
We can quibble over what exactly is part of the sensory information.
We can also quibble over what "sensory information" is even meant to be.
But it should be uncontroversial that we gain information from our
senses. My point is that, on any plausible way of spelling this out, the
information we receive is centred: it doesn't have parameters that fix a
unique location in space and time. If I were unsure about what time it
is or who I am, looking at the wall in front of me wouldn't help. The
underlying reason, of course, is that photoreceptors are insensitive to
differences in spatiotemporal location: they don't produce different
outputs depending on where or when they are activated by photons.
I wrote this short
piece for a special issue of the Journal of Consciousness Studies on
Chalmers's "The Meta-Problem
of Consciousness" (2018). Much of my paper rehashes ideas from section 5 of
my "Imaginary
Foundations" paper, but here I try to present these ideas more simply and
directly, without the Bayesian background.
My paper "Imaginary
Foundations" has been accepted at Ergo (after rejections from
Phil Review, Mind, Phil Studies, PPR, Nous, AJP, and Phil
Imprint). The paper has been in the making since 2005, and I'm quite
fond of it.
The question I address is simple: how should we model the impact of
perceptual experience on rational belief? That is, consider a
particular type of experience – individuated either by its
phenomenology (what it's like to have the experience) or by its
physical features (excitation of receptor cells, or whatever). How
should an agent's beliefs change in response to this type of
experience?
Earlier this year, I read Tyler Burge's Origins of
Objectivity. It's a very long book. Here is an abridged version. A few comments below.
Origins of Objectivity
Representation is a basic explanatory kind in psychology that should
be distinguished from mere information-carrying. The most fundamental
type of representational state is perception. In perception, an
organism attributes properties to objects in its environment. To do
this, the organism does not need linguistic capacities, nor does it
need to know (or otherwise represent) necessary and sufficient
conditions for being the relevant object. Instead, the science of
perception reveals that it is sufficient that the organism stands in a
suitable causal relation to the object and that its perceptual state
involves certain constancies (for shape or colour or distance or
whatever) which characterize the object "objectively", abstracting
away from contingencies of the present stimulus.
I like the starting point — to think of intentional states as
explanatory scientific kinds. Burge doesn't say
what exactly he means by this. I would put it as a kind of
functionalism: intentional states are characterized (at least
in part) by their functional inter-connections and their relationship
to environmental causes, behaviour and other psychologically relevant
facts.
Colours are physical properties of external objects. One such colour
is Pure Green: the shade of green that looks not at all yellowish or
blueish. However, if people are asked to identify the shade of green
that looks not at all yellowish or blueish, they come up with
(slighly) different shades: what looks pure green to me looks slighly
blueish to you; what looks pure green to you looks slightly yellowish
to me. What shall we make of this?
We could claim that one of the groups is simply right about Pure
Green and the other wrong, even though there is no way to find out which is which. That is incredible.
For the "Philosophische Club" at the university of Bielefeld, I've made a short paper out of that entry on perceptual content. The proposal is still that the information we acquire through perception is the information that we have just those perceptual experiences. But more needs to be said about what that amounts to: if "having just those experiences" means having experiences with this fundamental phenomenal charater, the proposal is incompatible with physicalism; if it means having just this brain state, the proposal is false. So I end up defending a kind of analytical functionalism even about demonstratives like "this experience". The main argument has something to do with skeptical scenarios. I won't repeat it here, as the paper itself is short enough.
Looking out of the window, I come to believe that it's snowing
outside. I don't just add this single belief to my stock of beliefs; I
conditionalize on something. On what?
It doesn't seem to be the proposition that the scene before my eyes
contains the very features that caused my perception. Arguably, what
caused my perception is H2O falling from the sky. If that was what I
conditionalize on, I would take my present experience as
evidence that snow is made of H2O, rather than XYZ. But I don't.
One can think of perception as a relation between states (or acts) and objects, the objects that are perceived. Alternatively, one can think of it a relation between a state and a content, the information acquired or represented in the perception.
Content is something that excludes possibilities. Suppose I have a perception of an elephant standing in front of me. What possibilities are thereby excluded? There are at least two reasonable answers: 1) the exluded possibilities are possibilities where there is no elephant in front of me; 2) the excluded possibilities are possibilities where I do not have that experience. Regarded as sets of possible situations, on the first account, the content of my perception is a set of situations in which there is an elephant in front of me. On the second, it is a set of situations where I have the phenomenal experience I actually have, even if it is caused by evil scientists. (Strictly, "I" need not be me, but can be whatever is in the center of the relevant situation.)