Sacred is an adjective (Random House Dictionary, 1967). It would seem that one cannot let te word simply dangle: it must refer to something (as in: the sacred land; the sacred text.) Yet the (translated) title of Rudolph Otto's famous book is:
The Idea of the Holy.
True, it obviously is a Germanism. The (relevant part of the) original title is:
Das Heilige.
Has that form now become commonplace enough so that I may speak of "The Sacred" as in the title I am contemplating, for a paper discussing interpretation of sacred texts:
"On Reading the Sacred"?