Whooo....quite the hot thread here. I don't really want to get directly involved, I'm actually just going to toss this bit of fat into the fire.
It's interesting that people like and use definitions of objects, topics, genres, time periods, measurements, etc. to identify commonly related items. Over the centuries, we've realized the value of such commonality as it assist us in communicating with one another even in different languages, cultures, and eras. We can read and translate older texts and understand them without the need for a rosetta stone, even though our languages continue to evolve and change.
A natural progression of such sorting is that it has to start somewhere and it then grows and evolves (or dies and is assumed into something else or is lost), based on the opinions of authorities prominent at the time. Relatively speaking, science (separate from any arcane or supernatural connections) on the whole is still very new in our history, only about 400 years or so of open study. So science fiction and any sub-genres it may (or may not) have are even newer; only in existence this last century.
No matter how gray a sorting or grouping of things begins, it naturally evolves into a very black & white argument such as we see here in this discussion because it is entirely subjective. Someone, somewhere had to make a decision to classify a story/book/show as science fiction or fantasy which works fine until they encounter a square peg in the pile and just have to make a call on it, whether or not it fits. No doubt new genres may be created by someone like the Library of Congress to sort books that may later better fit these types of stories but until then what are they really? It becomes quite subjective at that point, thought most of the time we can all agree which barrel they should be in.
The reality is that there are no black & white definitions, just whatever is generally accepted and understood, which of course will change with the next generation of viewers or shows comes along, challenging all we believe and know.
Rigel
