Some Parallels

In Poul Anderson's Technic History:

one Chereionite telepath works for the Merseians;

a dying Marine says, "'...don't eat me, mother...'" (Captain Flandry, p. 306);

the Ardazirho remind Flandry of wolves;

he interrogates one by sensory deprivation.

In Jerry Pournelle's and SM Stirling's "The Asteroid Queen":

the kzinti are feline;

a few are telepathic;

Harold interrogates one by sensory deprivation;

when allowed to speak, the interrogated kzin says, "'DON'T EAT ME MOTHER...'" (Man-Kzin Wars III, p. 133).

Thus, a few parallels between two future histories. If we assume parallel universes, whether as a fictional premise or as a scientific theory, then there must be some laws governing the parallels. L Sprague de Camp suggested that periods when many world-lines intersect might be periods when it is easier to be transported into the past. Similarly, parallel events might occur at moments when it is easier to travel between universes.

Inter-universal travelers will expect other worlds to be like theirs. A DC Comics super-villain, when told that there was one Earth where no one had acquired any superpowers, thus that in that world the only place to read about superheroes or super-villains was in comic books, not in newspapers, remarked, "Seems unlikely..."

All The Alternative Histories

Is there a catalogue of alternative histories anywhere? We know who the main writers are and what the main themes are. Roy Tully in SM Stirling's Conquistador (New York, 2004) summarizes two:

"'...I know the concept. South wins the Civil War, Hitler wins World War Two, that sort of thing. Been some pretty good movies that used it.'" (p. 177)

There are other obvious themes:

Alexander the Great lived longer (Poul Anderson, Greg Bear, SM Stirling);
different outcomes in 1066 (?);
no Reformation (Kingsley Amis, Philip Pullman);
a successful Spanish Armada (Keith Roberts);
Oliver Cromwell lived longer (a DC Comics Elseworld) -

-and less obvious:

aliens invaded Earth during World War II (Harry Turtledove);
Mars and Venus were terraformed long ago (SM Stirling);
someone discovered how to degauss the effects of cold iron (Poul Anderson).

Bring The Jubilee by Ward Moore begins as a Confederate States alternative history but ends as a causality violation time travel novel, thus showing the degree of overlap between these two sf themes. Did Bring The Jubilee influence Anderson's "Time Patrol"? Anderson could not remember. However, conceptually, Bring The Jubilee does belong in a sequence of precursors to the Time Patrol:

Mark Twain, A Connecticut Yankee...;
HG Wells, The Time Machine;
L Sprague de Camp, Lest Darkness Fall;
Moore, Bring The Jubilee;
Anderson, "The Little Monster" and "The Man who Came Early."

An involuntary time traveler prospers and makes changes that do not last;
the Time Traveler invents the Time Machine and his dinner guests discuss anachronisms on battlefields like Hastings;
a second involuntary time traveler prospers and makes lasting changes;
a time traveling historian unintentionally diverts the course of a decisive battle;
a third involuntary time traveler survives but a fourth comes to grief;
the Time Patrol is founded to prevent accidental or deliberate historical changes.

In Anderson's "The House of Sorrows" and also in the deleted timeline of his "Delenda Est," Christianity does not get started whereas, in his Westfall timeline, Christendom exists but is destroyed. In all three timelines, Europe remains divided into small warring states practicing polytheism. The difference is that the Westfallers eventually develop science.

A Conceptual Sequence

Seven works by six authors form not a linear series but certainly a conceptual sequence that could with profit be read in this order:

"Missing One's Coach: An Anachronism" (Anonymous)
A Connecticut Yankee In King Arthur's Court by Mark Twain
The Time Machine by HG Wells
Lest Darkness Fall by L Sprague de Camp
Bring The Jubilee by Ward Moore
Past Times by Poul Anderson
The Time Patrol series by Poul Anderson

Several other works, including three further novels by Anderson, are also closely connected. However, the listed seven are significantly sequential, culminating in one collection, one omnibus collection and one long novel by Anderson. These three volumes draw together strands introduced in the earlier works.

"Missing One's Coach" introduces the idea of a modern man transported backwards through time into a historical period. It might have been a dream but the idea is there. Pastwards travel is essential for time travel. Without it, the Time Traveler would have been unable to return.

Twain develops this idea of a modern man transported to an earlier period but seems not to realize, first, that it would have been difficult to introduce technological innovations in the Dark Ages and, secondly, that it would have been impossible to introduce at one stroke modern technology in such a period. Twain's successors, de Camp and Anderson, spell out this difficulty and impossibility.

Wells:

introduces the idea of a temporal vehicle or "time machine," which reappears in a more versatile form in the Time Patrol series;

discusses the appearance of a time traveler on a historical battlefield, an idea developed by Moore and Anderson;

 
hints at temporal paradoxes, examined in one novel each by de Camp and Moore and in a lengthy series by Anderson;

colorfully describes future periods as Anderson colorfully describes past periods;

as a pessimistic Victorian, describes the devolution of humanity whereas the optimistic American Anderson refers to its evolution;

shows the Time Traveler exploring the further future as an Anderson character does in "Flight to Forever."

For his first Time Patrol assignment, Manson Everard travels from the year in which The Time Machine was published to post-Roman Britain in order to prevent a "time criminal" from pulling a Connecticut Yankee stunt back then. Anderson's "The Man who Came Early," which should be included in future editions of Past Times, is a reply to Lest Darkness Fall whereas "The Little Monster," which is in Past Times, presents the de Campian view: a modern man can survive in the past. Thus, the conceptual sequence progresses and culminates with Anderson.

The Barbarian

Poul Anderson's "The Barbarian" IN Anderson, Fantasy (New York, 1981), pp. 148-158, is an insightful satire.

Conan stories and novels are decipherments, by Howard, de Camp and their successors, of pre-Pleistocene inscriptions. One preglacial people were horse nomads or maybe Centaurs. Serpens was ruled by snake worshipers or possibly by snakes.

A wandering barbarian adventurer would lack civilized values and virtues. His wars would be merely destructive, not also diplomatic. Tireless himself, he would march his troops so fast that they outran their supplies and were too exhausted to fight. He would lack finesse in both social and sexual intercourse. (Some) women would run towards him but even faster away from him. He would alienate allies and depress the economy by destroying wealth. The most prudent course for any civilization is to ensure that he supports their enemies, not them!

This satire is followed by an essay on heroic fantasy which I will reread next.