The noetic hindrances， also called "hindrance by the known"， hindrances of the knowable， as well as known as "hindrances to wisdom" 智障 （jn~eya-a^varan!a）. . These are the subtle hindrances of cognition， based primarily on a lack of full penetration into the principle of the emptiness of elemental constructs. In more everyday terms， it means to be hindered from attaining enlightenment by none other than our own knowledge， our own habituated way of knowing. That is， it is exactly what we think we know， which keeps us from enlightenment. The concept is originally developed in Yoga^ca^ra texts such as the Yoga^ca^rabhu^mi-/sa^stra 瑜伽师地论， Maha^ya^na-sam!parigraha-/sa^stra 摄大乘论， etc.， but can also be found in later East Asian works such as the Awakening of Faith 起信论 and Sutra of Perfect Enlightenment 圆觉经. These hindrances are taught along with the afflictive hindrances 二障--the hindrances by karmically habituated passions. while the afflictive hindrances can be mostly eliminated by the contemplation techniques of the practitioners of the two vehicles， the most subtle of the noetic hindrances are only eliminated by the advanced compassion and wisdom of the bodhisattvas. They are referred to together as the "two types of hindrances." The most concentrated discussion of the Two Hindrances is to be found in Wonhyo's Doctrine of the Two Hindrances （Ijangui: 二障义）.