[sgc]

> what I call "red" could be very different to someone else's subjective perception

It's worth noting that is true of virtually everything we know. >>This is a very simple sentence.<< Anybody who understands English, 'understands' it. But what it means to understand it is perhaps completely different for each person. As long as they fit into the same place in their worldview (Lewis Caroll's Carrollian syllogisms come to mind), practically it often doesn't matter beyond recognizing the wonderful uniqueness of each human being. Likewise, unless somebody is color blind or perceives more colors than others (tetrachromats), it doesn't matter since the relationships between the different concepts or colors will be analogous amongst most people - so a common understanding within the differences is possible. Or perhaps it is more precise to say that there are so many data points in color perception or anything we know, that despite the minor differences in relationships, we understand each other because the differences must be minimal given the practically unlimited data points constraining our perceptions. In fact, when people's perceptions of things vary too much, they can be classified as mentally ill even if they understand many things perfectly well.

[sysguest]

> As long as they fit into the same place in their worldview

but... "same place in their worldview" model goes awry when things to slightly off course

most people are ok with calling rgb(255,0,0) red, but some will argue with rgb(200, 50, 20)

[patapong]

At the same time, there's some commonality for what words mean in different contexts. For example, even though we all have our own experiences with the concept of "dog", there's a common core where we have enough of an understanding what other people refer to as "dog" to allow discussing the concept. Likewise, for most people, dog is more similar to cat than to house.

Imagine if we could build a machine that reads a bunch of texts and tries to extract this meaning by looking at which words commonly co-occyr with other words in different contexts. Perhaps something interesting would happen...

[TheOtherHobbes]

Yes, but the qualia could be completely different and we'd never know.

For all I know you don't just have a completely different experience of red, but a complete different experience of geometry and spacetime.

Your subjective experience of vision could be a mirror of my own. But we'd both still associate "right" with the same half of the body.

You might not "feel" curves and lines the same way.

As long as everyone's mappings and weights are identical, the qualia themselves could be anything.

We assume the qualia would at least be recognisable, and they can't be too different because there has to be a common core of experience categories, with recognisably consistent relationships.

But beyond that - anything works.

This isn't a hypothetical because once you get into politics and ethics, the consistent relationships disappear. There are huge differences between individuals, and this causes a lot of problems.