In the 14th century part of our current read, The Dream of Scipio, Olivier de Noyen encounters two “heretics” and learns of their beliefs, one of which is reincarnation. In the novel, this is traced back to the 5th century protagonist Manlius, his philosophical treatise on The Dream of Scipio, and his philosopher friend Sophia.
As in so much in the novel, there is a grain of truth to it, and we were reminded of the Cathars, which were quite familiar to some in our reading group. Wikipedia (handle with care as usual) has an extensive article on Catharism, with a number of external links, one of which is Cathars and Cathar Beliefs in the Languedoc (Cathars and the Cathar Crusade: history, cathar theology, crusade leaders, explanations, maps and source documents).
Under section # 3.3 Eschatology in the Wikipedia article it says:
‘The goal of Cathar eschatology was liberation from the realm of limitation and corruption identified with material existence. The path to liberation first required an awakening to the intrinsic corruption of the medieval “consensus reality”, including its ecclesiastical, dogmatic, and social structures. Once cognizant of the grim existential reality of human existence (the “prison” of matter), the path to spiritual liberation became obvious: matter's enslaving bonds must be broken. This was also suggested by the philosopher Plato, who suggested “forms.” This was a step by step process, accomplished in different measures by each individual. The Cathars clearly accepted the idea of reincarnation. Those who were unable to achieve liberation during their current mortal journey would return another time to continue the struggle for perfection. Thus it should be understood that reincarnation was neither a necessary nor a desirable event, but a result of the fact that not all humans could break the enthralling chains of matter within a single lifetime.'
There are still people today who profess to be Cathars and/or descendants of Cathars.’
There are plenty of books available on Cathars, and some group members were familiar with this literature. I myself have read only one book, several years ago, and I'm still racking my brain about the title…
The above image represents Cathars being expelled from Carcassone in 1209.