There was corruption in the medieval church, Hildegard asserted, and he, as pope, should be doing something about it.

Hildegard did not hold back her anger; but among her many complaints, she included an unusual throw-away comment – a reference to one of the greatest mysteries of her life: she told Anastasius that she had witnessed a miracle, an experience that led her to create Unknown Letters and to speak an Unknown Language (lingua ignota and litterae ignotae in Latin). 

These mysterious creations remain little understood today, and scholars continue to debate their purpose.