大乘起信論裂網疏 3.7

3.7

東西定方，以喻真如。如其定方而正了知，以喻覺義。迷東為西，以喻不覺妄念。方非迷悟，為迷悟依，悟方之時，方外別無悟相可得，以喻如外無智；迷方之時，方外別無迷相可得，以喻真如之外別無妄念，是故妄念自無實相也。

East and west as fixed directions are a metaphor for tathatā. Correctly understanding in accordance with their fixed directions is a metaphor for the meaning of enlightenment. Confusing east for west is a metaphor for the deluded thoughts of non-enlightenment. The directions are neither delusion nor awakening, but serve as the basis for delusion and awakening; when one awakens to the directions, outside of the directions there is no separate mark of awakening to be apprehended, which is a metaphor for there being no wisdom outside of suchness; when one is confused about the directions, outside of the directions there is no separate mark of delusion to be apprehended, which is a metaphor for there being no deluded thoughts outside of tathatā; therefore, deluded thoughts themselves have no real mark.