大乘起信論裂網疏 4.62

4.62

Defilement is interrupted only upon attaining Buddhahood; this is what is called ignorance having no beginning yet having an end. Purity is ultimately uninterrupted; this is what is called initial enlightenment having a beginning yet having no end. Both defilement and purity rely on the original enlightenment of tathatā; this is what is called original enlightenment having neither beginning nor end. For example, relying on cardinal directions, delusion occurs; delusion and directions are both beginningless. Relying on delusion, awakening occurs; awakening and directions are both endless. Outside of directions there is no separate delusion or awakening; outside of delusion and awakening there are also no separate directions. Because immutable directions necessarily accord with the two conditions of delusion and awakening, tathatā is itself arising and ceasing; because the two conditions of delusion and awakening can never alter the directions, arising and ceasing is itself tathatā. Yet in delusion one opposes the directions and every step is errant, while in awakening one conforms to the directions and comes and goes at will; therefore one must reverse delusion and return to awakening.