Sentence:  And although these insights into the nature of art may be in themselves insufficient for a thoroughgoing philosophy of art , their peculiar authenticity in this day and age requires that they be taken seriously and gives promise that from their very substance , new and valid chapters in the <WSD>philosophy</WSD> of art may be written . 
Meaning of the word marked with <WSD> tags:  a belief (or system of beliefs) accepted as authoritative by some group or school