Plato on the Madness of the Muses

It might be so if madness where simply an evil; but there is also a madness which is a divine gift, and the source of the chiefest blessings granted to men. … The third kind is the madness of those who are possessed by the Muses; which taking hold of a delicate and virgin soul, and there inspiring frenzy, awakens lyrical and all other numbers; with those adorning the myriad actions of ancient heroes for the instruction of posterity.

-Plato’s Phaedrus