The 2021 theme for a french competitive philosophical exam is: "the common". I'm not sure the expression really makes sense in English. In French, it is the adjective "commun" ( English. common) used as a substantive.
Bibliographies that have been proposed by university departments so far concentrate on the political aspect of the notion: the common versus what is owned as an individual property. One very common notion of common in economics is the Tragedy of the Commons. Sociologists are very interested broadly in the notion of community. Other angles to investigate might be common sense and common knowledge. So the theme does not seem to have a real unity, but, rather, is split into as many forms of "common" as there are various subjects to which the term applies.
The problem I am asking is: Is there one fundamental problem linked to this notion, that is, to "the common" or " common-ness" as such?.
Which philosophers and theories reflect on the general idea of "common-ness" at the fundamental level, is there any ontological/metaphysical theory of "common-ness"?