"Mussorgsky you very rightly call a hopeless case. In talent he is perhaps superior to all the [other members of The Five], but his nature is narrow-minded, devoid of any urge towards self-perfection, blindly believing in the ridiculous theories of his circle and in his own genius. In addition, he has a certain base side to his nature which likes coarseness, uncouthness, roughness. He flaunts his illiteracy, takes pride in his ignorance, mucks along anyhow, blindly believing in the infallibility of his genius. Yet he has flashes of talent which are, moreover, not devoid of originality."
January 1, 1970
https://en.wikiquote.org/wiki/Modest_Mussorgsky