Diana, Carolina, Ana and David asked:

Until now, most of the people believe and accept several standards of classification and distinction
among everything that surrounds us. For example, we classify colors, figures, objects and even
sensations. Nevertheless, philosophy has questioned how equanimous is the actual appreciation
each one of us has about things. For instance, it is known that red is red because it emits a certain
kind of light, but how do we know that two or more different persons conceive or appreciate in the
same way such color? Or maybe two persons can say they feel "happy", but it could happen that they
are experiencing totally different sensations. Then, is there a way for measuring the appreciation or
sensations (emotions) of a person to compare them with someone else's?

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We don't and cannot know purely subjective facts about others' sensations and experiences so we
could not measure them. It is logically possible that sensations differ but unlikely that they differ much
in fact. Although we cannot measure or compare sensations or even know what it would be to do this,
we change can another's sensation. Often you can look at a colour, for instance, and call it green and
when another person points out that it is blue, your qualia changes as you come to see it as blue.
Another such case is when a colour blind person sees two taps as completely grey and then sees a
red dot on top of one when he finds the water is hot.

The same is true for happiness. One can question a person's claim to be happy through dialogue by
looking at definitions of happiness, joyousness, pleasure, contentment etc through which is possible
to change someone's own assessment of their state as well as their actual sensation. Because of our
shared physical nature and language, the objective or social enters into, defines or categorises
subjective sense experience, but conceptual knowledge by means of which we define sensations is
not the qualia itself.

If we were to try to measure and compare sense experiences, falsification would arise because the
terms of measurement will always be conceptual and physical rather than psychical. Physical
measurement requires a specific quantity, but there is no point at which my green qualia changes to
blue because this is a process rather than a quantitative objectively assessable item.

Rachel Browne

I don't believe there is any way to measure the way different people experience things (these are, by
the way, known as "qualia" in technical philosophical terms). However, if we believe that science
gives us a reasonably good explanation of the way the world works, and we believe that it is
necessary to grow up in a community of humans in order to become a human person (and I think
there are good reasons for believing both), then we can use an argument to the best explanation to
say that others are like me in how they work, so they are (most likely) experiencing qualia just as I
am. This is short of a proof, but I think that we just have to accept it.

Tim Sprod