Matthew asked:

I was wondering about reality and perception. Is what we perceive considered to be reality. Take for
example color. Light is projected at certain waves and frequencies, each one of these differences the
human brian interprets as a different color. Many would argue that those are the true colors of the
frequencies. But what about people that are color blind, they perceive those colors differently. What if
everyone perceives colors differently?

If the colors just a human's interpretation of reality, thus varying from person to person, and therefore
"real" to each individual person. Can we have true knowledge on what colors really look like?

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Generally, yes. What we take to be reality is that which we perceive. Colour is, of course, difficult.
Locke called colour a secondary quality, as opposed to a primary quality, since it's perception is
reliant on a creature with the ability to sense. Today, many would say colour is not a part of reality
because the sensory aspect, what red "looks like" is a fact about consciousness of a certain sort of
being rather than a fact about the world.

However, we understand facts to be what makes up reality and some people talk of mental facts.
There is a theory of consciousness (see Ted Honderich's web site) called "mental realism" which
relies on the fact that we cannot deny that consciousness is real for us, and so it is part of the world.
On this view, our sensory experiences are part of reality even if we were to experience colours
differently — and it is logically possible that this is the case, whereas it is not possible that we see
square as round because we would then move around in the world inappropriately. Frank Jackson
("Epiphenomenal Qualia", in Philosophical Quarterly32) also argues that the world is not just the
physical world. He tells a story about a woman who learns all about the world from a black and white
television and when she finally leaves her room and enters the world she learns a new "fact", i.e.
what it is like to experience red. This sort of mental realism allows colour experience to be a part of
reality, but it is compatible with everyone having different colour experiences.

A physicalist, who believes all that is real must be physical would agree with your suggestion that
colour perception is a matter of light waves and frequencies and brain processing but once again this
is compatible with varying sense experiences.

So whether sense experience is part of reality or not doesn't help us to answer how we can know
what colours really look like. But you mention colour-blindness and this is an interesting case. My
husband has trouble with red and blue. Once, in a hotel room, he looked at the taps and both looked
grey. On turning the taps on to find which was hot and which cold, the spots on the taps turned from
grey to provide a sensory experience of red and blue. This is quite common in colour-blindness. It
seems to indicate that knowledge of what a grey spot should look like plays a part in providing an
experience of red or blue. I would say that there are regularities and connections in the brain. My
husband hasn't always had the grey experience and so probably past experiences where he had
immediately sensed red and blue came to the fore through memory and connection to provide the
correct neural response to the light waves. So I suppose that when we receive certain waves and
frequencies, a specific neural state is necessary for an individual to sense red in the same way
across time.

However, whether the phenomenal "look" differs for each individual, we cannot know because
consciousness is private.

Rachel Browne