[otai]

Originally Posted by Sute443

That's because causal loops, in addition to being fun, are the most likely form of time travel to be used by any writer who bothers to think about things in any form beyond "RAAR!! Change past make big boom!" That is, if the writer cares about using time travel intelligently (i.e.: making sense), causal loops are usually the best method to use.

Spoiler for Book 4 madness:

Speaking of causal loops, at the end of Book 4 Kyon cannot stop Yuki from changing the world; he is supposed to let her change it first, then change it back.
Since the first attempt from the past failed, there is a second attempt from the future that succeeds. 2 causal loops and 3 Kyons from 18th December.

Future Kyon returns to the future,
Stabbed Kyon wakes up in a hospital on the 21st
The Kyon sleeping at home either a) wakes up in an alternate dimension, or b) he vanishes while walking down the stairs at school.

a) Means all 3 Kyons are simply different positions on the same world line; and even though the world is restored, Yuki still created an alternate dimension just for Kyon to maintain the loop. It also means there was a Kyon clone interacting with the normal SOS-dan on the 18th. Or maybe a Yuki->Kyon Marionette.

b) Means that there is a alternate Kyon somewhere out there...

And also the funny idea that Yuki threw a comatose Kyon down the stairs.

Yuki: It is all right. Inertial dampeners activated.