Within genre, there are at least two different modes of multiverse: one where the multiverse is relatively mapped out, as in H. Beam Piper’s “Paratime” fiction (1948–65); and the other where the multiverse is unknown to all except the discerning reader, as in a cryptic series beginning with
The Dark World (1946) by Kuttner and Moore.
“Paratime” is about a multiverse where time travel seems to happen as one visits a different universe where history followed a different route. For example, there is the “Aryan-Transpacific sector” where the Indo-Europeans went east, through Asia to North America. The point being that what looks like “time-travel” is actually dimensional travel (hence the term “paratime”), a distinction which deftly avoids time paradoxes. Access is by flying saucers. This multiverse is being patrolled by the Paratime Police, who right wrongs, but above all they preserve the secret of Paratime.
This mode is more science fictional, and Wolfe uses it in its “pioneer” form (i.e., a lone inventor creates a portal to another dimension) in a number of cases I will not list, to avoid spoilers.
In contrast,
The Dark World is a case of a man from our world being drawn to another dimension through a portal he does not understand. The same sort of thing happens in the couple’s other novels
Valley of the Flame (1946),
Lands of the Earthquake (1947),
The Mask of Circe (1948), and probably others. This device is used for a variety of subgenres:
The Dark World explores a fantasy world of warring wizards;
Valley of the Flame is a South American exploration adventure;
Lands of Earthquakes has Crusaders in a trippy landscape that moves around a lot, making maps pointless; and
The Mask of Circe is set in classical Greece.
This mode of multiverse is more “magical,” and Wolfe uses it in
There Are Doors, at least. I will refrain from naming others.
To consider the situation in
The Book of the New Sun, start with a provocative line from the BayCon audio-only interview (1982), where Wolfe says, “[People of Urth] have interstellar travel, which we do not have . . . [and] means of reaching parallel universes, which we do not have” (17:20).
BayCon interview (1982)For context, this is limited to TBONS. “Interstellar travel” is clear enough, but “parallel universes,” in essence, “multiverse,” is tricky to parse. On the largest scale, it would definitely apply to the Briah/Yesod situation (a two-universe solution). Building on this by adding a more ambiguous area, it probably also includes the magic mirrors drawing and sending beings elsewhere (which might mean there are three universes, or wide open to many universes).
So far, so good: the lines between the different universes are clear, and egress across the barriers is possible only through elite machinery (a starship or magic mirrors).
But what if “multiverse” also applies where it is not expected? What if the Botanical Gardens of Nessus offers doorways to “paratime,” and there is no time travel
in the Gardens at all? This would avoid time-paradoxes by casual visitors to the gardens, lest there be a “Sound of Thunder” disaster every week, if not every day. Because the barrier crossing is invisible, it seems like a Dark World mode; but because we know the architect is Father Inire, it has a “Paratime” feel to it for being choice locations selected among many, curated by an authority.
In that same interview, a few seconds later, Wolfe is talking about the energy weapons in use on Urth and how Severian lacks the technologist vocabulary to tell us whether they are masers or lasers. That is in play here, the lack of distinction between time travel and dimension travel; but with the gardens, the problem is on our side, as readers, since we recognize the 20th century in the jungle garden, whereas Severian definitely does not.
To back up: within TBONS I am trying to separate out the strands of “implies time travel” and “demonstrates time travel.” There is a big difference in access to a public park, and walking a certain maze at a certain time to reach the Last House; there is a big difference between a theme park seeming real, and the upper floors of the Last House looking out onto an ice age foretold. I am trying to establish how there might be a lot less time travel than initially thought; that the Botanical Gardens are something like training wheels, to get the reader prepared for the weirdness of the real thing.