When I [Bryan Magee] asked him [Bertrand Russell] who he regarded as the greatest man he had ever met, he needed longer to consider his reply. In the end he came up with Lenin. When I asked why, he said it was because Lenin combined a brilliant mind with genius-level ability as a man of action, and this gave him extraordinary stature and effectiveness as a person. Also, he had changed the entire course of world history in a way few individuals ever do. However, he added, Lenin was not in the least morally admirable: he came near to boasting about the enormous scale of the death and suffering he was causing, and laughed about it in conversation with Russell.
Communists Didn't Mean Well
Confessions of a Philosopher, by Bryan Magee, p 208-209:
“'Don’t be so sure—nobody can be certain of anything.' Bertrand Russell’s gibberish to the contrary notwithstanding, that pronouncement includes itself; therefore, one cannot be sure that one cannot be sure of anything. The pronouncement means that no knowledge of any kind is possible to man, i.e., that man is not conscious. Furthermore, if one tried to accept that catch phrase, one would find that its second part contradicts its first: if nobody can be certain of anything, then everybody can be certain of everything he pleases—since it cannot be refuted, and he can claim he is not certain he is certain (which is the purpose of that notion)."
- Ayn Rand
Philosophy: Who Needs It (http://aynrandlexicon.com/lexicon/certainty.html)