Infinite temporal flux

According to the Tenth Doctor, the mechanics of the infinite temporal flux worked much like the basic conceit of Back to the Future. In the same way that Marty McFly began to fade out of existence because of changes to his family's personal history, it was possible for whole civilisations to expire by tampering with the past. Essentially, the term meant that much of time was always in flux, and that protecting the past was vital to preserving the future. (TV: The Shakespeare Code (TV story)) It was therefore a complementary theory to that of the so-called "fixed point in time".