Side line: “kata sarka” (according to the flesh) must be taken as adverbial, it qualifies verbs for “knowing” – how they know or in this sense not knowing – “not according to the flesh.”

「凭血」（﹕凭外貌；意思﹕凭肉体）﹕是副词，指「道」、「认」人这动词。他们如何认（认）﹕「凭肉体」。