He regarded the questions 'Sekishunokoe' (the sound of one hand clapping) and 'Kushibussho' (a question asking whether it is possible for a dog to have the Buddha nature or not), which enlightened him, as the most important of all the koan.
中でも自らの悟りの機縁となった「隻手の声」と「狗子仏性」の問いを、公案の第一に位置づけた。