When asked why he wrote music, a composer once answered that it was because there was music inside his head that didn't yet exist. Writing it gave it existence.
It has been said of the French existentialist thinker, Jean-Paul Satre, that he was, arguably, at his freest while under German occupation. His subversive action was to write.
The composer Gustav Holst once commented that he wrote now so that later he would write better.