So, as far as I know, there are several series approved by Asimov or his estate for the Foundation series, including the Second Foundation Trilogy and the Caliban Trilogy.

Of the Robot/Empire/Foundation novels, I've only read the Foundation series so far, but I was wondering—are either the Second Foundation Trilogy or the Caliban Trilogy considered canon within the R/E/F universe? If not, are they treated more as fanfiction (but approved!) or in some sort of in-between state?

  • 1
    What does 'canon' mean in this instance? It's not like Asimov himself will be writing more works in that universe...
    – user1027
    Commented Jan 24, 2012 at 3:15
  • @Keen Canon as in—are the information and events in them considered to be part of the fictional universe? For example, if you were answering a question here, would you cite those novels as evidence or would you consider them closer to the fanfiction end of the spectrum?
    – waiwai933
    Commented Jan 24, 2012 at 3:27
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    Check out en.wikipedia.org/wiki/Foundation_series#The_Foundation_Series This will give the rundown on to complete series including the other authorized authors. Commented Feb 8, 2012 at 21:08

3 Answers 3


I don't think Asimov kept things as neat and tidy as you would like. His stories all follow a similar arch through the future, but I don't know that he ever worried himself on stating if any particular book was "canon" or not.

Later books ("Foundation's Edge", "Foundation and Earth", and "Forward the Foundation") were written by Asimov, albeit much later in his life, so I guess I would consider that canon.

The "Second Foundation Trilogy" was written by Benford, Bear, and Brin; and "Isaac Asimov's Caliban" by Roger Macbride Allen, so I would not call these books canon and put them more in the "fan fiction" category.

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    The second trilogy was not written by Asimov. It was written by Benford, Bear, and Brin, some years after Asimov died. Commented Jun 27, 2012 at 18:05
  • @Remiel is correct; have edited this answer to include this. Commented Mar 19, 2013 at 2:02
  • @neilfein - What are we considering the "Second Foundation Trilogy"? By that I meant "Foundation's Edge", "Foundation and Earth", and "Forward the Foundation", then there is still "Prelude to Foundation", but those were all written by Asimove. Benford, Bear, and Brin wrote another 3 Foundation books that I was not referencing, please change my answer back.
    – Justin C
    Commented Mar 19, 2013 at 3:26
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    The books by Benford, etc were officially called the Second Foundation Trilogy, and Asimov never wrote anything by that name. If you don't like my edit, please go ahead and revert it, but be aware that your answer had incorrect information in it before. Perhaps my additional edit will help clarify this? Commented Mar 19, 2013 at 3:50
  • @neilfein Agreed. Asimov wrote one trilogy, two sequels that ended with an unresolved cliffhanger, and two prequels. The only thing ever called the "second trilogy" is the Benford/Bear/Brin trilogy. Commented Mar 19, 2013 at 12:33

There is no clear answer to this, and probably never will be. If you're looking for an official word on what's canon and what isn't, or perhaps even levels of canon as there are in Star Wars, you'll not find anything like that with Asimov's works. And as you'll see, this may have been left deliberately open to interpretation.

Also, this isn't a case of a large franchise with someone passing down edicts, it's a different situation entirely. Asimov's works can almost certainly be considered canon, but there's really very little guidance after that. But we can apply reason:

The stories in the multiple-author anthology "Foundation's Friends" were written while Asimov was alive, but are of questionable "canon". Some of the stories set in the Robot/Foundation/Empire universe even contradict Asimov's stories. The tone of much of this book seems to be one of affectionate pastiche more than an attempt to add to Asimov's body of work. Similarly, the Robot City books (which I haven't read) appear to be more of an attempt to riff off of the concept of Asimov's robots.

Roger MacBride Allen's trilogy of books about the robot Caliban is a bit of a special case: The good doctor approved outlines for these books before he died, so an argument could be made for including them in the Asimov canon. Additional books by Mark W. Tiedemann and Mickey Zucker Reichert were approved by Asimov's estate, but Asimov himself had nothing to do with these. The "Second Foundation Trilogy" by Greg Bear, Gregory Benford, and David Brin was also authorized by his estate, but the series was conceived after Asimov's death.

Asimov himself was fond of linking his works together, but left gaps in what was "official". The books Nemesis and The End of Eternity may or may not be linked to the Robot/Empire/Foundation books - and the author was tantalizingly ambiguous about their status.

He also clearly had no issues with others extending his work; Robert Silverberg wrote three novels that were expansions of Asimov stories.

Asimov's fiction was also a small part of his output; he wrote many non-fiction books, and was particularly passionate about his volumes popularizing science. Education was clearly important to him. He was also very supportive of new writers - he wrote several essays on how he became a published author, with advice for others on the same path - and he considered intelligence and imagination to be of paramount importance.

A lack of any official body to set canon means that readers are free to determine the canonicity of these works on their own. It seems to me that this is exactly the way Asimov would have wanted this: Readers using their imaginations to decide on canon.

  • Not only was the Caliban trilogy approved in outline by Asimov, but IMHO it's written very much in his style, is filled with his concerns and his logic, and dovetails so neatly with his books that I can't help considering it part of his universe. (They're also some of my favourite books — heartily recommended!)
    – gidds
    Commented Jul 26, 2023 at 11:52

Canon is only meaningful in the context of more authors writing more material, and being obligated to maintain consistency with what came before. Since the Asimov estate is not interested in more Foundation works being published at this time, what is canon and what is not remains to be determined. If they decide to authorize more works, it's up to them to decide what is canon at that time. If they don't, it doesn't matter anyway.


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