The term "national idea" is an unclear one. One might think of it as a widely shared understanding among a people as to the desired way of life in their country, an idea that holds sway over the population. A unifying concept like that can be useful, but should never be created artificially or imposed top-down by the powers-that-be.
Aleksandr SolzhenitsynLiterature transmits incontrovertible condensed experience... from generation to generation. In this way literature becomes the living memory of a nation.
Aleksandr SolzhenitsynWhen I was in the gulag I would sometimes even write on stone walls. I used to write on scraps of paper, then I memorised the contents and destroyed the scraps.
Aleksandr Solzhenitsyn