As Nietzsche himself indicates, “what the word ‘idols’ on the title page
means is quite simply what had been called truth so far” 

Philosophizing with a Hammer - another great title!

Although the work is “a little light adventure into a psychologist’s idle hours” 
the philosophical import of Nietzsche’s theses is anything but light; it marks
nothing short of a conceptual revolution in Western thinking whose impacts
 were felt throughout Western culture in the twentieth century

The key to Nietzsche’s criticism of the Western philosophical tradition’s rationalism is his
identification of a twofold movement: the denigration of reality, regarding it as a secondary world of appearances, and the positing of a fictional “true” world of ultimate value to justify this denigration.