I have two questions.
1) Why is there a comma in the following line:
"the work of art, are identified"
2) What is/are the subject of "are identified" in the previous sentence?
Here is the full excerpt for context:
"Dickie is here developing a direction pointed to in the other (and earlier) of the two most influential writings in institutional theory, “The art world” by Arthur Danto (1964) (to which I will return). There, what Danto calls “the atmosphere of theory,” and the historical relatedness or relational properties of the work of art, are identified as essential conditions for arthood."
Source: I have got these lines from a textbook on art theory.