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.” 「凭血气」(中译﹕凭外貌;意思﹕凭肉体)﹕是副词,指「知道」、「认识」人这动词。他们如何认识(或不认识)﹕「不凭肉体」。
In grammar an adverbial (abbreviated adv) is a word (an adverb) or a group of words (an adverbial phrase or an adverbial clause) that modifies or tells us something about the sentence or the verb. (The word adverbial itself is also used as an adjective, meaning "having the same function as an adverb".) Look at the examples below: