成唯識論演祕 7.89

7.89

答：理亦可成。而本論云：「由是遍計所緣相故」者，釋曰：由依他起，能起第六能遍計心，方執離識實我、法等。若不有此依他之境，能計不起。能計不起，何有所執遍計性耶？由斯二性故不異也。亦猶於繩方起蛇覺。餘准可知。

Answer: In principle it can also be established. As for the root treatise stating, "Because it is the objective nimitta of that which is imagined," the explanation says: Due to the paratantra, the sixth mind capable of imagining is able to arise, and only then clings to a real self, real dharmas, and so forth separate from consciousness. If this paratantra object did not exist, that which imagines would not arise. If that which imagines does not arise, how could there be the imagined nature (parikalpita-svabhāva) that is clung to? It is because of this that the two natures are not different. It is just like the cognition of a snake arising only on the basis of a rope. The rest can be understood by analogy.