The second pass goes like this: Jealousy is an emotional reaction to something that's going on. Like anger and disappointment, it's an emotional indication that not all is right, and one that's common in relationships of all sorts. If we can figure out the root cause of it, we can address the problem and fix the symptom and all will be well again. We don't have to be afraid of being jealous on occasion as long as we deal with it and don't let it be a caustic thing, or handle it badly if/when it comes up. Denying that we feel jealousy if we do could be very destructive, because it would put off addressing the underlying issue(s).
This second pass is what I see around polyamory websites, and I find it very valuable. Me being me, I have a third pass, which pulls jealousy apart into two sub-categories.
One kind of jealousy I see is "That is mine and you can't have it.", or alternately "I don't have that and you do and I wish to take it from you (so I have it and you don't)". It's what could be called possessive jealousy. It's the kid on the playground lusting after the toy his brother is playing with. It's seeing your partner holding hands with someone and being consumed by possessive green envy. It is "this should be mine and only mine."
The second kind is gentler, though not necessarily any less intense. It's "I see that you have this and I want it too". It's the kid on the playground seeing other kids with ice cream and begging his mother to get him some too. It's seeing your partner holding hands with someone and going "wow, can she do that with me sometime?" The key difference is that with this kind of jealousy, you want to have something, but you don't need everyone else to stop having it so you can. I'm going to call this suggestive jealousy.
Both of these responses are natural and useful. Possessive jealousy is good for pointing out problems that need to be addressed. This site explains that very well, so I'll leave you with that link and move on. What I really want to talk about is suggestive jealousy, and how useful I've been finding it.
Suggestive jealousy is useful because it shows me what I want. I've had this problem where I want something, but I don't know exactly what it is that I want. Specifically, I want physical intimacy with Hats (and, to a lesser and fluctuating extent, Flowers), but I don't know what specific actions will satisfy that desire and also be comfortable for us and our relationship. This isn't a case of not knowing if it would be okay to do a particular thing, it's a case of having a nebulous craving and not knowing which particular things will fulfill it.
What does this feel like? Say that you've never heard of cookies, but you want something sweet to eat. Candy? No, you want something baked. Pie? No, that's too mushy. Cake? No, you really want something chewy that you can hold in your hand and take bites out of. Like Candy? No...no, you guess cake is really what you want, even though it's kinda big and messy. So you have a piece of cake and try to convince yourself that that's what you wanted, because its the thing that fits your criteria the best. You couldn't say 'No, I want cookies' because you'd never heard of cookies. But if you saw a cookie, you would immediately realize that that's exactly what you wanted to eat.
I see three ways to go from this situation. First is the lazy option. You eat the cake and try to convince yourself that you're satisfied, because that's the thing that's closest to what you wanted, right? But as anyone who's ever had a food craving knows, that may work some of the time, but it's not the most satisfying solution.
Second is the very effort-intensive option. You bust out the apron and bake batch after batch of sugary messes, trying to invent a cookie without knowing what it looks like or how its done. Eventually, if you are persistent, you will emerge triumphant with your new creation, and that will be pretty awesome, but that takes a lot of work and a LOT of failed batches of cookies which you must scrape sheepishly into the compost, or force yourself to eat even though they are really sub-par.
The third option is a middle ground between laziness and effort. You take tours of bakeries, peering at all the shelves and sniffing the air until one day you spot in the back corner a rack of cookies and go 'AHAH! That's what I want!'. This is what I am trying to do with touch. There are a lot of ways to be physically intimate out there. Just in my everyday life and in my chosen media, I see dozens of examples of affectionate/intimate touch. This is me wandering around the bakery. So how do I pick out the things I like? Suggestive jealousy. It would take an enormous amount of thought-energy and reflective patience to carefully analyze each instance of physical affection to determine whether it's something I want. Fortunately, suggestive jealousy is the feelings equivalent of a big flashing neon sign in a bakery, pointing at a plate of cookies and mouthing 'over here'. It makes me perk up and go 'yes, that!'.
So when I watch Hats kiss the top of Flowers' head, or see the two of them cuddle in a new configuration, I am jealous, but it's not that I want them to stop doing that, or that seeing those actions makes me feel bad. It makes me feel good, both because they're happy, and because it points out to me something that I want, which I can then articulate, which I can (probably) then get. It's actively useful to me. They're happy, I'm happy, and I don't have to do all the work of figuring out intimacy from scratch. Everybody wins.
Note: I originally wrote this post when I was living near Hats and Flowers and seeing them very often. I tweaked it a tiny bit for tenses and to use the new names, but nothing more. This active process of figuring out touch is on hold while I'm away at school and out of touch-range, but the suggestive jealousy has turned up in a different light. Now it serves as a good measure of how touch-starved I am. I've found that I miss touch quite a lot when I'm away at school, and how much I miss it varies depending on my stress level, how long it's been since I visited Hats and Flowers or talked to them, the weather, and so on. Watching how jealous I am when other people hug each other is a good way to keep track of it.