Eternal return

Eternal return, (PROSE: The Eternal) also known as cyclical time, (PROSE: Diamond Dogs) was the concept that history repeated itself in similar forms countless times. (PROSE: The Eternal) By some accounts, this was how Gallifreyan history and also time generally functioned. (PROSE: The Infinity Doctors, Cold Fusion)

Indeed, "the same patterns turn[ed] up all over space-time", which explained the similarity between Haitian voodoo and the Faction Paradox. Another example was the similarities between the life stories of the Doctor and the Devil, which were so great that some cultures believed them to be one and the same. (PROSE: Interference - Book One)

By one account, the Doctor's time stream was an eternal recursive spiral in the Ocean of Time, which branched off into New Selves. Through this, the Doctor had far more than just 13 lives. (COMIC: Vortex Butterflies)

An ancient Gallifreyan proverb stated that “Time moves in circles”, (PROSE: Lungbarrow, The Infinity Doctors) which was literally true due to the shape of time being a coiled spiral. (PROSE: The Infinity Doctors) The Pythia, originators of the proverb, (PROSE: Lungbarrow) believed that reincarnation existed on Gallifrey before regeneration. (PROSE: Cat's Cradle: Time's Crucible)

By some accounts, regeneration was introduced with the invention of looms at the end of the Intuitive Revelation. The artificial nature of the loom-born created a timeless stagnancy in Time Lord culture, such that little changed in the following millions of years due to every generation being made from the same template. (PROSE: Cat's Cradle: Time's Crucible, Lungbarrow, The Infinity Doctors) Every generation of Time Lord society initially possessed a spirit of ambition towards a golden age of progress which eventually faded as Gallifrey fell back into tradition and change was forgotten before the pattern repeated. (PROSE: The Infinity Doctors) Ultimately, the society into which the First Doctor was loomed had the same structure and institutions as the society which Rassilon established ten million years earlier. (PROSE: Cat's Cradle: Time's Crucible, Lungbarrow, The Infinity Doctors) This pattern would continue beyond the Doctor's lifetime, with even the final generation of Time Lords, the Children of Kasterborous, being said to fit within it. (PROSE: The Infinity Doctors)

Even monumental events such as Gallifrey going to time war seemed to be caught in this repetition, with aspects of the ancient Time Wars bearing notable resemblance to the Millennium Wars and War in Heaven. (PROSE: The Infinity Doctors)

Some time travellers would notice that they sometimes repeated the exact same events in different contexts. (PROSE: Dear Friend, WC: Shadow of a Doubt)