In a koan (a Zen question for use in meditation) within the 'Hyakujonoyako,' the second rule of 'Mumonkan,' there is a story about an old man who lived in Mt. Hyakujo in a previous life who claims that those who have once reached enlightenment do not 'fall into inga (cause and effect; karma).' Instead, by concentrating only on a state of 'ku' (emptiness) and ignoring the principle of inga, they fall into a state of chikushodo (the realm of animals) as a yako for five-hundred lifetimes.
「無門関」第2則の「百丈野狐」の公案には、前世に百丈山にいた老人が、かつて覚った者は「因果に落ちない」と言い、「空」の境涯のみを持ち上げて因果の理法を無視したが為に、五百生の間、野狐身の畜生道に堕したという話がある。