俱舍論疏 30.34

30.34

On the Śāstra's statement: "Observing the questioner [...] whether tortoise hair is hard or soft": The author of the Śāstra replies. Our school says that the aggregates are nominally called the self. While the aggregates are the self, the non-Buddhists falsely cling to a separate, real self that is identical to or different from the aggregates. Since the self does not exist, identity and difference cannot be established, and therefore the Buddha did not declare it. It is just as one would not answer whether tortoise hair is hard or soft; answering it would be an irrelevance, failing to address the premise of the question.