"Speaking of the young C.C. members, I wish to say a few words about Bukharin and Pyatakov. They are, in my opinion, the most outstanding figures (among the youngest ones), and the following must be borne in mind about them: Bukharin is not only a most valuable and major theorist of the Party; he is also rightly considered the favourite of the whole Party, but his theoretical views can be classified as fully Marxist only with great reserve, for there is something scholastic about him (he has never made a study of the dialectics, and, I think, never fully understood it)."
January 1, 1970
https://en.wikiquote.org/wiki/Nikolai_Bukharin