In 1865, Jules Verne's _De la Terre à la Lune_ was science fiction. By 1903, Tsiolkovsky made it space fantasy. By 1960, it was back to science fiction again, though it will never be usable for manned launches until we find some way to make >100g accelerations survivable.
As such, I don't find it useful to divide the genres too strictly. A Charles deLint fairy tale novel and a Cunningham/Carruthers Men in Black comic are in the same genre: low modern urban fantasy. Laser guns and magic wands are the same thing. Lightsabers and vorpal blades are the same thing. Robotic automata and servitor daemons are the same thing.
In most cases, the fantasy elements keep the story interesting, and the sci-fi elements lend it an air of future plausibility. You don't have to explain a magic wand, but you might have to mention that a laser rifle uses an Er:YAG laser and a heavy air-breathing lithium battery, only in very arid atmospheric conditions, to literally explode the water in a human target into steam from hundreds of meters away. But a shock cannon uses a different type of laser to ionize the air between the user and the target, and uses a voltage multiplier circuit to shoot an artificial lightning bolt down the conductive pathway, grounding through the target. If it isn't explained, it's another magic wand.
I have read books that started out looking like high fantasy at the beginning, until the characters learn that magic is the result of an AI--from the colonization ship's navigation computer--performing weapons research on the human descendants of its former passengers, and that the creatures formerly described as demons are actually aliens.
Try to pigeonhole that one into the right genre.
(For the first half of the description, I was sure I knew what it was, but hesitate to say so out loud because that would be a spoiler.)
That's an interesting view, but one which is nullified by:
> There's no definition of "science fiction".
Then the phrase has no meaning or use, and the statements "Star Wars is science fiction" or "space opera is a subgenre of science fiction" are semantically null, neither true nor false, just sequences of words that form grammatically valid sentences that communicate no meaning.
If "space opera is a subgenre of science fiction" is to be true, then "space opera" and "science fiction" both need to have definitions, and the definition of the latter must include at least everything included in the definition of the former. If either or both has no definition, then the statement has no meaning, and cannot be said to be true or false.
For
* The written definition, as found in the dictionary and/or agreed upon by the tiny subset of hardcore fans who care.
* The loose popular definition, which varies for each person but tends to include the broadest set of common basics: lasers, robots, spaceships, etc.
When referring to the written definition, it makes sense to say, "It's space opera, which is a subgenre of science fiction," as long as you're saying it among folks who appreciate the distinction. But when referring to the popular imagination, it's not a stretch to say, "There's no definition of "science fiction," because it means something a little bit different to each person.
The words "science fiction" mean something. They're a map pointing to some territory. They don't mean the exact same thing to everyone, but close enough to be useful.
Attempted definitions of "science fiction" attempt to point at the meaning. They're maps pointing to a map.
When I say "there's no definition", what I really mean is "I've never seen a definition that points to a good map of the territory".
In particular, a lot of definitions point at maps which don't point to Star Wars, and those are bad maps.
"definition" and "meaning" are the same thing.
> You don't need to be able to define a word, to know roughly what it means.
The degree to which you know what a word means is precisely the specificity to which you can define it. Those are different phrasings of the same content.
> The words "science fiction" mean something. They're a map pointing to some territory. They don't mean the exact same thing to everyone, but close enough to be useful.
I kind of disagree with this. The words "science fiction" mean different enough things to different people (and even to the same people in different contexts) that those definitions are not close enough to be useful, except where social convention, mutual agreement, etc., act to align the definitions to, if not precise alignment, very close alignment within some very narrow subset of the space of all the definitions the term has when considering all possible contexts of use.
Often, a key aspect of making the term useful in a particular exchange is agreeing on a definition.
> When I say "there's no definition", what I really mean is "I've never seen a definition that points to a good map of the territory".
I think the problem is that you fail to recognize that the different uses aren't various fidelities of "maps" pointing to the same "territory", they are -- to borrow the map/territory metaphor -- maps pointing to different territories that are share a name, the way the same name might refer in different contexts to the juridical territory of a city, the territory of the county of the same name in which the city is located, the territory of a metropolitan area centered on the city that is not coextensive with it or the county, or a geographical feature associated with and overlapping the boundaries of the citiy. A map of any of those territories would differ critically from the other, not because it is a bad map of the territory, but because it is a map of a different but overlapping territory.
> In particular, a lot of definitions point at maps which don't point to Star Wars, and those are bad maps.
I think its a bad map in the way that a map of Los Angeles that doesn't include East L.A. [0] is a bad map.
[0] An unincorporated community in Los Angeles County, but not part of the City of Los Angeles.
Given that I've explained the distinction I'm making, this is a super unhelpful thing to say. It makes me disinclined to engage with the rest of your comment.
It's space opera, which is a subgenre of science fiction.
Some people invent definitions of "science fiction" that exclude some works of science fiction, but that's silly. There's no definition of "science fiction". It's a concept that we feel out by pointing to things that are "clearly science fiction" and then sort of deriving a fuzzy decision boundary from that. If you ask people whether Star Wars is science fiction, most people will say yes. Robots! Lasers! Space ships! Aliens! It's clearly science fiction.
There are useful definitions, which talk about subsets of science fiction that don't include Star Wars. But those aren't definitions of science fiction, even if they use the same words.