Hm...
The story didn't really draw me in, except in regard to what was probably an unintended theme (more on that later). I've never cared for 2nd person narration, so that was certainly a factor. I didn't really feel like, for most of the story, there were significant stakes that I cared about--just living for traveling to weird worlds and then suddenly it all hits home when the voice starts going away. The Silent ones, despite being the title element, never really made sense to me even when the character became one. Why do they go silent? What does that have to do with the red orbs? Do they ever actually accomplish anything against the red orbs, or do they just mill around looking kindof weird and then disappear?
After the story
OK, I like the high-level concept of putting us in the position of the natives of the New World after the Europeans arrived. And there was the hint that unquestioning tolerance might actually make us vulnerable, which if intended might be something of a controversial (if potentially true) stand to take.
Maybe that's what the author was thinking for a theme. That wasn't what my brain latched onto though.
This story, "The Silent Ones," is a good example of how every listener can come out of it with a very different perception.
And boy howdy, can it ever be interpreted differently! And apparently no one else has yet interpreted it the way I did.
When they started talking about permanent residents from other dimensions by immediate thought was "okay, this is a story about immigration". My brain latched more onto more of a position of the point of view of Americans in the face of immigrants from any other country. I'm going to assume that's not what the author intended but that's what I latched onto.
The aliens show up. No one fights them. They become more abundant and start to become a part of society in some way, and though they mostly keep to themselves and are tolerated because they're not causing any kind of obvious harm, their presence starts shifting the status quo (change in architecture) and people don't really worry about them all that much and they even start thinking that they can hold positions of authority (running for congress). The only people who have the foresight to sense the threat of these aliens are rendered mute and eventually invisible (by them disappearing from the dimension entirely).
If this theme were the intent (and I don't think it was) then it could be interpreted as an anti-immigration cautionary tale: Don't complacently allow these people to come into your country and start taking the jobs you don't want right now so that you can go immerse yourself into your frivolous entertainments, because in your complacency these immigrants will become citizens, or at least their children will become citizens, and then they'll start voting, and then they'll take over your country right from under your nose and if you have the gumption to speak back against them you'll be ostracized for your intolerance. What we must do is to never be complacent, to fight their presence as soon as they arrive!
Like I said, I don't think that was the intent, but once that got into my head it was a hard interpretation to shake, and nothing in the story really gave it a push in another direction for me. I'm the only one who's mentioned this so far, so this is apparently not a common interpretation.
The great thing about science fiction is that you can take any theme and make it into a story that may not be about real-world issues in any significant way, can make people think about real-world events from an entirely different perspective through the clever use of themes, allowing them to shed some of their long-held baggage long enough to gain some fresh perspective.
The flip side of this coin is that, unless the story beats one over the head with a Moral, which tends to result in a story that is less effective and less popular, the theme has to be tied closely into the narrative and is probably largely subject to interpretation, and some of those interpretations might be the polar opposite of anything the author was actually meaning to convey. I try to be very careful to avoid saying "the author meant to say ____" because unless I can quote the author explicitly saying that, it's all interpretation, it's all subjectivity.