Now it remains only to show what the conception grace of the highest miracle, seeks in the greatest holy heater with last love-meal in sacred vessel flowing as longed for by the Knights. What in short — is the Graal!
But Parsifal does not ask in the first act: What is the Graal, Parsifal asks, Who is the Graal? — and why does Wagner not have Parsifal say: What is the Graal? — Here lies hidden a profound mystery! So Parsifal asks (with underlying intent of the author): Who is the Graal? — and Gurnemanz answers quite revealingly: That one does not say!

II. Main Part : The Unveiling of the Secret. - Parsifal and the Secret of the Graal Unveiled (1914)