大乘起信論義記 2.32

2.32

疑者又云：以何得知依妄念生？釋云：以諸聖人離妄念故。既無此境，即驗此境定從妄生。又若此境非妄所作、定實有者，聖人不見，應是迷倒；凡夫既見，應是覺悟，如不見空華，應是病眼。返結準之，故云若離於念則無等也。

The doubter further says: "How is it known that they arise relying on delusional thoughts?" In explanation, [the author] says: Because all the noble ones are free from delusional thoughts. Since they are without these objects, this verifies that these objects definitely arise from delusion. Furthermore, if these objects were not produced by delusion and were definitely real, then the noble ones' not seeing them should be an error of confusion, while ordinary persons' seeing them should be awakening—just as, if someone does not see flowers in the sky, they would have diseased eyes. Reasoning by contraposition, it is therefore said, "if one is free from thoughts, there are no..." and so forth.