Circularity in The Corridors of Time

We appreciate the ingenuity of circular causality paradoxes in time travel fiction but usually forget the details. Here, I summarise the paradoxes in a 1965 novel by Poul Anderson. I have omitted some details because they do not bear directly on the paradoxes.

Rival regimes called "Wardens" and "Rangers" from two thousand years in our future wage war through time and are the real cause behind historical conflicts like Catholics and Protestants or Cavaliers and Roundheads. They cannot change their past but hope, by manipulating social trends and subtly altering the balance of forces, to influence their future from which they are barred by their successors.

The Warden, Storm, tries to lead an attack into the Ranger homeland by driving a new time corridor through from the twentieth century. However, the Ranger, Brann, already informed about the new corridor, leads a counterattack down the corridor. Storm escapes alone and hires a twentieth century man, Lockridge, to accompany her to 1827 BC and the Danish village of Avildaro where they can await a ship to Iberia and thence to the Warden base in Crete. When an Aryan war party approaches Avildaro, Lockridge persuades Storm to stay and defend the village with futuristic weapons. He and she become prisoners of Brann who leads the war party with superior weapons and captures the village.

Brann predicts that Lockridge will change sides because it was he who had informed Brann of the new corridor and the flight to Avildaro. Lockridge escapes and brings Wardens who capture Brann and free Storm. Lockridge must then travel to the era of Wardens and Rangers and pretend to defect to the Rangers in order to tell Brann about the new corridor and Avildaro. Threatened with painful interrogation to confirm his story, he escapes and returns to Avildaro where Storm plans to build a Warden base in Stone Age Northern Europe by supervising the intermarriage of Sea People, from villages like Avildaro, with the Aryans.

Lockridge cooperates despite the unhappiness of his friends among the Sea People. Wardens Storm and Hu fly on gravity belts to investigate a large fleet approaching from England. In their absence, Lockridge finds that Brann is still alive but being painfully interrogated by the Wardens. On their return, he confronts them and is held under guard but he and a group of villagers escape when the English fleet attacks. Before leaving, Lockridge frees Brann from the interrogation machine so that he will die quickly. Lockridge leads his people to England twenty five years earlier, builds a progressive federation that he already knew of and leads the fleet that attacks Avildaro. Lockridge's wife from Avildaro, who returns with him, sees their younger selves fleeing from the village. Storm, captured, is bound and confined in the house from which she had ruled where she is strangled by the dying Brann who has just been freed by the younger Lockridge. Lockridge's confederation builds Stonehenge of which, of course, Lockridge had known in the twentieth century.

Comments

How easy is it to "escape" when held captive? Lockridge does it three times. The third time makes sense because his captors are under attack. If he had not escaped from Brann in Avildaro, then Brann would not have known to attack Avildaro. If Lockridge had not escaped from the Rangers in their own era, then their "psychic probe" would have extracted the truth from him. In that case, the Brann who had counterattacked in the time corridor and who had captured Avildaro would have known that he was to be captured and would have ordered other Rangers to recapture Avildaro as soon as Lockridge had departed for the Wardens' and Rangers' era.