There can now be no doubt that it is Stalin rather than Hitler, who is the most alarming figure of the twentieth century. I say this-I say this not merely because Stalin killed more people than Hitler-though clearly he did-and not even because of Stalin was more of a psychopath than Hitler-although clearly he was. I say it because Stalin was not a one-off like Hitler, an eruption from nowhere. Stalin stands in a historical tradition of rule by terror which existed before him, which he refined, and which could exist again. His, not Hitler's, is the spectre that should worry us.