The "ālaya-vijñāna" is also what experiences rebirth into future lives and what descents into the womb to appropriate the fetal material. Therefore, the "ālaya-vijñāna's" holding on to the body's sense faculties and "profuse imaginings" ("prapañca") are the two appropriations which make up the "kindling" or "fuel" (lit. "upādāna") that samsaric existence depends upon. Yogācāra thought thus holds that being unaware of the processes going on in the "ālaya-vijñāna" is an important element of ignorance ("avidya"). The "ālaya" is also individual, so that each person has their own "ālaya-vijñāna," which is an ever changing process and therefore not a permanent self. According to Williams, this consciousness "seen as a defiled form of consciousness (or perhaps sub- or unconsciousness), is personal, individual, continually changing and yet serving to give a degree of personal identity and to explain why it is that certain karmic results pertain to this particular individual. The seeds are momentary, but they give rise to a perfumed series which eventually culminates in the result including, from seeds of a particular type, the whole ‘inter-subjective’ phenomenal world." Also, Asanga and Vasubandhu write that the "ālaya-vijñāna" ‘ceases’ at awakening, becoming transformed into a pure consciousness.