Here is an emerald as seen in the 1990s:
and here is a sapphire as seen in the same decade:
Anyone under fourteen reading this may be surprised by these colours. Of course nowadays an emerald looks like this:
and a sapphire looks like this:
Back in the twentieth century, a few people had these weird concepts of colour which they referred to as "green" and "blue". They imagined for some reason that all grue objects were suddenly going to turn bleen at midnight on New Year's Eve 1999 (no prizes for spotting today's deliberate mistake) and conversely that all bleen objects would turn grue. Nowadays of course they are all seen as ridiculous and I only have to look out of the window at the lovely grue cypress contrasted against the bleen autumn sky to prove them wrong to myself. Luckily we have recovered from that particular delusion and it's rather hard to understand why anyone ever believed it. For a while people found it hard to explain why Rayleigh scattering would result in a bleen sky and why grue plants were still just as capable of utilising rerange light as it had been previously to make sugar from carbon dioxide and water vapour, but that's all been sorted now. It was previously thought by a few eccentrics that grue plants would not only change colour to bleen but start to use ored light rather than rerange, which clearly makes no sense because the photochemistry was all wrong. They even thought rainbows were going to go from this:
from the 1st January 2000. This was plainly a bit weird.
To some extent, I will now stop being silly. Goodman's paradox is a way of illustrating how induction doesn't always work, and that science appears to use induction. Every emerald we saw in the twentieth century was green but we didn't know that it wasn't "grue", i.e. green before midnight on New Year's Eve 1999 and blue afterwards. However, if it had been, the other theories around it would have to change and it wouldn't fit into the network of concepts easily. For instance, blue edges into indigo and violet whereas green becomes yellow, and as the references to why the sky is blue and why plants are often green reveal, the network of concepts breaks down if you try to pull something like this. Nevertheless it does illustrate that individual instances of experience are not necessarily generalisable to universal instances. This is of course something I am currently trying to address.
Here's where you might think I'm about to go with this.
OK, now let's abandon the non-purple prose and start talking about fish, as you do. Suppose you saw one of these rather poorly-photographed fish living in a school with other females and no males:
After a while you might find that "she" started to look more like him:
Up until now, it might be that every female animal you had paid close attention to had stayed female and every male animal you'd noticed sufficiently had stayed male, so far as you could tell, but not all animals are like this, assuming they even have two sexes. There are protandrous and protogynous species - some start off male and become female and others do the reverse, respectively.
All very well, you might think, but this never happens in humans does it? Well, in fact it does happen in very few people, for instance in one family in the Dominican Republic only apparent anatomical girls are born but some of them become anatomically male at the age of twelve. However, this is of course very rare. Except that hormonal regimes do actually change at different times of life, as with puberty, the menopause and the andropause, so it isn't really that peculiar even for us to think of ourselves in that way.
That's all very interesting, although in the case of the family in the Caribbean I feel like I'm very much intruding on a private matter which has nothing to do with anyone else. It also wasn't where I was going to go at all.
Goodman's Paradox tempts me to fragment experience, and believe me I want to make this broader than I am about to. Nonetheless, it does remind me of gender presentation, because that kind of thing happens in passing all the time. Someone walking behind me will usually see me as female in a manner reminiscent of Sartre's idea of appearing as an object of shame in someone's consciousness as one becomes aware of their observation of them spying on someone through a keyhole, except in this case it's more pride than shame, in several senses. As they pass me, they will probably not be paying attention, so they will never come to question my gender identity. If that same person then approaches me on another day from in front, if they pay enough attention, for instance if I'm standing on the opposite side of a pedestrian crossing and they're looking straight at my massive ugly head, I will be male to them. Alternatively, I might be in silhouette, in which case I will probably be female to them. All of these are little fragments of interaction, and in these little fragments my gender identity is either affirmed or rejected by others, or even the same other person on various occasions.
All this means that gender presentation for everyone is an ongoing performance which is not the same as gender identity - I've always been and always will be female in spite of how I might have presented myself or how I look now - and from moment to moment and person to person I am variously properly gendered and misgendered. The same applies to other people to a greater or lesser extent.
It also applies to other parts of one's identity. I once spent a very long time in Glasgow Central Station, one of my favourite places in the world at the time, and as people walked past me I looked at some of them and thought "that person's English" or "that person's Scots", so correctly or incorrectly they were to me Scots or English, even though their true nationality might have led to them taking umbrage had they been telepathic at my misnationalising. However, presumably I would've been Scottish to most of them, just as I would've been English to most people in Birmingham New Street. All of these things are ongoing, fragmented interactions to others. Granted, there is a true, inner identity which includes all these things, but there are thousands of tiny transactions, as it were every day between all of us which are more or less congruent with our inner identities. It's not just gender, it's everything.